heinemann - ipt textbook

G.K. Powers

H e i n e m a n n

Information Processesand TechnologyInformation Processesand Technology

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Q W E R T Y U Y I O P Q W E R T Y U Y I O P Q W E R T Y U Y I O P

A S D F G H J K L : ” A S D F G H J K L : ” A S D F G H J K L : ”

Z X C V B N M < > ? Z X C V B N M < > ? Z X C V B N M < > ?

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9

ISBN 0-86462-512-X

780864 625120

You can visit the Heinemann World Wide Web site at

hi.com.au or send email to [email protected]

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HSC COURSE

Heinemann Information Processes and Technology:HSC Course has been written to meet all of the

requirements of the new Information Processes and

Technology syllabus in NSW. This text will help students to

develop their understanding of information processes in the

context of different information systems. It is designed to

build on the knowledge and skills gained in the Preliminary

course and to help students become confident, competent,

discriminating and ethical users of information technology.

This text provides up-to-date information, a practical

approach, and a large number of questions that cater for a

wide range of students.

Key features• list of outcomes and overview at the beginning of

each chapter

• social and ethical issues and Internet activities integrated

throughout the book

• numerous practical tasks that can be used with any

software or make of computer

• case studies and examples of information systems

• learning activities to help students apply the content in

every section

• chapter review at the end of each chapter

• interesting IT facts and cartoons to promote class

discussion

• key terms highlighted for quick reference

• glossary

• index.

Additional resources to support and extend this book are

available at Heinemann’s World Wide Web site, hi.com.au.

These include a sample teaching program, assessment

advice and answers to exercises from the textbook.

About the authorGreg Powers is a head teacher with many years’ experience

in writing and implementing computing studies programs.

He is the author of several highly successful texts including

Computing Studies–An Introductory Course.

Also availableHeinemann Information Processes and Technology:

Preliminary Course

ISBN 0 86462 501 4

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1 2 3 4 5 6 7 8 9 0 - 1 2 3 4 5 6 7 8 9 0 - 1 2 3 4

Q W E R T Y U Y I O P Q W E R T Y U Y I O P Q W E R T Y

A S D F G H J K L : ” A S D F G H J K L : ” A S D F

Z X C V B N M < > ? Z X C V B N M < > ? Z X C

! @ $ % ^ & * ( ) _ ) _ + ! @ $ % ^

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Q W E R T Y U Y I O P Q W E R T Y U Y I O P Q W E R T Y

A S D F G H J K L : ” A S D F G H J K L : ” A S D F

Z X C V B N M < > ? Z X C V B N M < > ? Z X C

! @ $ % ^ & * ( ) _ ) _ + ! @ $ % ^

G.K. Powers

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HSC COURSE

Information Processesand Technology

Heinemann

HeinemannA division of Reed International Books Australia Pty Ltd22 Salmon Street, Port Melbourne, Victoria 3207World Wide Web hi.com.auEmail [email protected]

Offices in Sydney, Brisbane, Adelaide and Perth.Associated companies, branches and representatives throughout the world.

© Gregory Powers 2000First published 20002003 2002 2001 200010 9 8 7 6 5 4 3 2 1

Copying for educational purposesThe Australian Copyright Act 1968 (the Act) allows a maximum of one chapter or 10% of this book, whicheveris the greater, to be copied by any educational institution for its educational purposes provided that thateducational institution (or the body that administers it) has given a remuneration notice to Copyright AgencyLimited (CAL) under the Act.

For details of the CAL licence for educational institutions contact CAL, Level 19, 157 Liverpool Street, Sydney,NSW, 2000, tel (02) 9394 7600, fax (02) 9394 7601, email [email protected].

Copying for other purposesExcept as permitted under the Act, for example any fair dealing for the purposes of study, research, criticism orreview, no part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or byany means without prior written permission. All enquiries should be made to the publisher at the address above.

Publisher: Rosie AdamsEditor: Liz JacobsenDesigner: Giulia De VincentisText designer: Giulia De VincentisCover designer: Relish DesignIllustrator: Guy HoltPhotograph researcher: Janet Pheasant

Typeset in 10.5/12.5 Berling by Palmer Higgs Pty LtdFilm supplied by Type Scan, AdelaidePrinted in Hong Kong by H & Y Printing

National Library of Australiacataloguing-in-publication data:Powers, G.K. (Gregory K.).

Heinemann information processes and technology :HSC course.Includes index.ISBN 0 86462 512 X.1. Information storage and retrieval systems. 2. Electronic data processing. 3. Information technology. I. Title

004

DisclaimerAll the Internet addresses (URLs) given in this book were valid at the time of printing. However, due to the dynamic nature of the Internet, some addresses may have changed, or sites may have ceased to exist since publication. While the authors and publisher regret any inconvenience this may cause readers, no responsibility for any such changes can be accepted by either the authors or the publisher.

iii

Contents

To the teacher vAbout the contributing authors vi

Part 1 Core 1

Chapter 1 Project work 21.1 Project management 41.2 Social and ethical design 81.3 Understanding the problem 121.4 Making decisions 151.5 Designing solutions 181.6 Implementing 261.7 Testing, evaluating and maintaining 29Chapter review 33

Chapter 2 Information systems and databases 352.1 Information systems 362.2 Organisation methods 422.3 Storage and retrieval 532.4 Other information processes 642.5 Issues related to information systems and databases 69Chapter review 73

Chapter 3 Communication systems 753.1 Characteristics of communication systems 763.2 Examples of communication systems 803.3 Transmitting and receiving 873.4 Other information processes 1003.5 Issues related to communication systems 104Chapter review 109

Part 2 Options 111

Chapter 4 Transaction processing systems Christopher Lean 1124.1 Characteristics of transaction processing systems 1134.2 Examples of transaction processing systems 1194.3 Storing and retrieving 1264.4 Other information processes 1344.5 Issues related to transaction processing systems 139Chapter review 144

Chapter 5 Decision support systems Quentin Evans 1465.1 Characteristics of decision support systems 1475.2 Examples of decision support systems 1525.3 Organising and decision support systems 1595.4 Processing and decision support systems 1675.5 Analysing and decision support systems 1715.6 Other information processes 1765.7 Issues related to decision support systems 179Chapter review 184

Chapter 6 Automated manufacturing systems Wayne Moore 1866.1 Characteristics of automated manufacturing systems 1876.2 Examples of automated manufacturing systems 1926.3 Collecting in automated manufacturing systems 1986.4 Other information processes 2076.5 Issues related to automated manufacturing systems 213Chapter review 217

Chapter 7 Multimedia systems Ellen Sheerin 2197.1 Characteristics of multimedia systems 2207.2 Examples of multimedia systems 2307.3 Displaying in multimedia systems 2387.4 Other information processes 2457.5 Issues related to multimedia systems 254Chapter review 258

Glossary 260Index 268Acknowledgments 274

v

To the teacherThis book has been written as a textbook for the New South Wales InformationProcesses and Technology HSC course.The aim of this course is to enable studentsto become confident, competent, discriminating and ethical users of informationtechnologies and information processes.This book addresses this aim and providesan excellent understanding of all aspects of information technology.

Even though students undertaking this course have satisfactorily completed thePreliminary course, they will vary substantially in understanding and skills. Thisbook has been written to cater for students with a wide range of knowledge levels.

Organisation of the textThe book closely follows the syllabus and the software/course specifications. It ispresented in two parts. Part 1 covers the first three components of the syllabus(60%). Each component occupies 20% of the course time. Part 2 covers the optionstrands (40%). Students are required to select two options. Each option covers20% of the course time.

• Part 1 Core1 Project work (20%)2 Information systems and databases (20%)3 Communication systems (20%)

• Part 2 Options (Students select only two options)4 Option 1: Transaction processing systems (20%)5 Option 2: Decision support systems (20%)6 Option 3: Automated manufacturing systems (20%)7 Option 4: Multimedia systems (20%)

Teaching programTeachers can decide on the sequencing of the content depending on the abilityand knowledge of their students.The first chapter on project work is fundamentalto the other chapters. Students need to cover this chapter early in the teachingprogram. Projects can be one large project or a number of smaller projects. Projectwork in the HSC course is intended to give students an opportunity to plan,design and implement an information system. The information systems chosenshould be one of the following:• a database information system• a communication system• a transaction processing system• a decision support system• an automated manufacturing system• a multimedia system.

The teaching program needs be consistent with the indicative times specifiedabove.

Additional resources to support and extend this book are available at theHeinemann World Wide Web site (hi.com.au).

vi

About the contributing authors

Christopher Lean is a programmer who develops and publishes software for hiscompany InfoVision. He has taught at TAFE level and at UTS and UNSW, and hasworked with a range of industries as a consultant.

Quentin Evans is an experienced teacher of Science and Computing Studies,having taught a variety of computer courses since 1986. She currently holds theposition of Computer Coordinator at Concord High School.

Dr Wayne Moore is a senior lecturer in computing at Charles Sturt University,Bathurst. He has been a mathematics teacher and science lecturer and currentlyteaches information technology to undergraduate and postgraduate students. Heconducts research in industrial control systems and robotics and has interests insimulation and virtual worlds.

Ellen Sheerin has been involved in teaching computing courses in schools since1985 and is currently Computer Coordinator at Gorokan High School. She hasbeen an HSC Computing Studies examination marker as well as presentingworkshops in computing for teachers.

Chapter 1 Project work

Chapter 2 Information systems and databases

Chapter 3 Communication systems

Core

11PROJECT WORK

cchhaapptteerr

• applies an understanding of the nature andfunction of information technologies to aspecific practical situation (H1.1)

• explains and justifies the way in whichinformation systems relate to informationprocesses in a specific context (H1.2)

• analyses and describes a system in terms ofthe information processes involved (H2.1)

• develops solutions for an identified needwhich address all of the information pro-cesses (H2.2)

• evaluates the effect of information systemson the individual, society and the environ-ment (H3.1)

• demonstrates ethical practice in the use of information systems, technologies andprocesses (H3.2)

• proposes ways in which information systemswill meet emerging needs (H4.1)

• justifies the selection and use of appropriateresources and tools to effectively develop andmanage projects (H5.1)

• assesses the ethical implications of selectingand using specific resources and tools (H5.2)

• analyses situations, identifies a need anddevelops solutions (H6.1)

• selects and applies a methodical approach toplanning, designing or implementing asolution (H6.2)

• implements effective management tech-niques (H7.1)

• uses methods to thoroughly document thedevelopment of individual and/or groupprojects (H7.2)

Outcomes

Project work for the HSC course follows the fivestages of the traditional system developmentcycle that were outlined in the Preliminarycourse. This chapter builds on these conceptsand includes additional content on prototypingand participant development. Students arerequired to construct an information systemusing the knowledge gained from this chapter.

Overview

Project work

In the Preliminary course, you were introduced to the system development cycle.It is a series of stages used in the development of a new information system.The traditional system development cycle has five broad stages (see Figure 1.1):1 understanding the problem—requirements of a system to solve the problem2 making decisions—feasibility of a new system to solve the problem3 designing solutions—creating the new system4 implementing—using the system to solve the problem5 testing, evaluating and maintaining—ongoing operation of the system.

Change in purpose

Change type of system

Change system

Change use of system

Understanding the

problem

Statement of problem

Type of new system

New system

Using new system

Problem with system

Makingdecisions

Designingsolutions

Implementing

Testing, evaluating

and maintaining

Figure 1.1 Stages of the system development cycle.

In the system development cycle, thereare four important features:• Each stage in the cycle is not always

separate and distinct. People involvedin the development of a new systemoften switch between stages.

• The cycle does not end with thetesting, evaluating and maintainingstage. It is a cycle, and the resultsfrom the final stage are used for theinitial stages of another new system.In this way the cycle is an ongoingprocess.

• The extent of the cycle depends onthe complexity and size of theproject. In a small project, some ofthe stages can be simplified andcompleted very quickly. However, ina large project, all the stages are moreinvolved. A large project usuallyrequires a detailed study of theexisting system and extensive workin the analysis and design stages.

• Each stage of the systemdevelopment cycle has certain tasksto be completed. It builds on theconclusions of the previous stages.However, there is often a goodreason to revisit the previous stages.

3

4 Core

1.1 Project managementProject management is the process of planning, scheduling and controlling all theactivities within each stage of the system development cycle. It aims to deliver anew system within an acceptable time frame and budget. Project managementinvolves creating a project plan.

Project plansA project plan is a summary of a project that specifies who, what, how and when.It clarifies what needs to be done and helps people to understand how they fit intothe project. A project plan usually breaks the project into major tasks calledsubprojects. It must provide an overall schedule, the details of the subprojects anda schedule for each subproject. It must also identify the people, informationtechnology and data/information required by the system.

A project plan is an important tool that helps to deliver a system on time andto minimise the effect of unanticipated problems. If a project has problems, theycan cause the schedule to be lengthened and costs to be increased.They could alsoforce the project to be reduced in scope, and this could affect the success of theproject. To minimise problems, people working on the project should understandthe need for project goals, deliverables and schedules:• Project goal—result of the project if it is successful. Goals may be broad, such

as creating a new system that works efficiently; or they may be very specific,such as developing a system within a budget of $150 000.

• Deliverable—a tangible item expected from a task. It may be a diagram, report,data dictionary, program or training manual.

• Schedule—the timing of major tasks and who will do the work. The success ofa new system depends on accurate time estimates for each task. A schedulethat doesn’t allow a reasonable amount of time for each task can actually resultin delays and additional costs.

IITT FFaaccttIT FactResearchers have found that 37% of software faults would have beenavoided by appropriate scheduling and reducing the stress on developers.

Project plans are constructed and managed using information managementsoftware and project management software:• Information management software helps individuals on a project to manage

information and schedule tasks. It allows email messages to be exchanged andorganised. Appointments, events and meetings can be put onto an electroniccalendar and viewed by the day, week or month. Information managementsoftware stores names and addresses of individuals and organisations.Tasks in theproject are assigned, sorted and organised.The progress made on tasks is seen ata glance.

• Project management software contains most of the features of informationmanagement software. It is a tool to efficiently plan, manage and communicateinformation about a large project (see Figure 1.2). Project management soft-ware allows projects to be joined, tasks to be split among team members andthe project to be tracked over the Internet or via email. It provides analysistools to assist with decision-making, such as ‘what if’ analysis.

Project work 5

One popular project management tool used to record and track schedules iscalled a Gantt chart.A Gantt chart is a bar chart with each bar representing a taskor stage in the system development cycle. The vertical axis of a Gantt chart liststhe tasks, and the horizontal axis shows the time frame (see Figure 1.3). Ganttcharts provide a quick method of determining whether the project is on schedule.They are used in meetings to review progress and identify problems.

Figure 1.2 Microsoft Project is an example of project management software.

Project plan

1 2 3 4 5 6Time (Days)

7 8 9 10 11

Evaluate existingsystem

Data collection

Prototype

Proposal—newsystem

Figure 1.3 Gantt charts help to record and track schedules.

6 Core

Communication skillsCommunication skills incorporate a variety of strategies and techniques fordealing with other people. Good communication facilitates the sharing ofinformation and genuine understanding. Some of the strategies for effectivecommunication are:• Active listening involves restating, reflecting and summarising the speaker’s

major ideas and feelings. Active listeners encourage the speaker and are non-committal.

• Conflict resolution solves arguments and disputes. It involves listening to theother person’s views and looking at the conflict as a problem to be solved.

• Negotiation skills involve discussing a problem and arriving at a consensus.They involve listening to different views and compromising to reach a solution.

• Interview techniques involve careful preparation, implementation and follow-up. A list of questions should be prepared with a clear purpose. Here are somegeneral rules for interviews:– Make the interviewee aware of the purpose of the interview.– Ask open-ended questions so that the interviewee must provide infor-

mation.– Check the responses by restating the interviewee’s viewpoint.– Try to be aware of the interviewee’s body language. It may be communi-

cating a different attitude.– Close the interview by reviewing the main points and thanking the

interviewee.– Review notes immediately and follow up with the interviewee on any

information that is unclear.• Team building is the process of getting a group of people working together.

Each team member negotiates a role in the team with specific responsibilities.The team members’ efforts are coordinated to ensure the efficiency of theteam.Communication skills are required by every person in the project.The number

of people involved in a project depends on its size and complexity. It includesinformation system personnel such as systems analysts and programmers. Systemsanalysts perform the analysis to decide whether a new or updated system willsolve the problem. They must be familiar with the organisation’s operations andthe latest developments in information technology and computer programmingtechniques. Systems analysts communicate their results to the programmers (seeFigure 1.4). Programmers convert a written description of a problem into a set ofprograms.They code programs and produce documentation. Both systems analystsand programmers work in teams and must be people with excellent communi-cation and interpersonal skills.

A large project may involve hundreds or even thousands of people. To managethe project, the organisation forms a project team and assigns the team to theproject.The team is responsible for the project from the beginning to the end. Theproject team consists of participants, systems analysts and programmers. Oneperson from the team is appointed the project leader. It is usually a systemsanalyst. A project leader (also called a project manager) develops schedules,checks work and resolves conflicts. He or she ensures that the project is meetingits goals.The project leader is responsible both for developing the project plan andensuring it is implemented correctly.

Project work 7

Figure 1.4 Systems analyst communicating with programmers.

Exercise 1.11 List the five stages in the system development cycle.

2 Why is the system development cycle an ongoing process?

3 How does the system development cycle differ between a small and large project?

4 What is a project plan?

5 Explain the difference between a deliverable and a schedule.

6 What is the purpose of information management software?

7 Why are Gantt charts a popular management tool?

8 List five strategies for effective communication.

9 Describe the role of a systems analyst.

10 What tasks are performed by a project leader?

LEARNING ACTIVITIES

1 ‘If each stage of the system development cycle is carried out properly, it should notbe necessary to return to the previous stage.’ Discuss this statement.

2 Describe one possible problem that might occur if the system development cycle isnot applied.

3 After one year of operation, an organisation had complaints from every depart-ment about a new information system. The new system contained a substantialnumber of errors. At what stage of the system development cycle is it easier andless expensive to identify and solve problems? Why? At what stage of the systemdevelopment cycle is it difficult and more expensive to identify and solve prob-lems? Why?

4 Why is it important to be able to return to the previous stage when developing anew system?

5 A project leader estimated a time schedule for the following tasks:– Write system design documentation: 2 weeks– Purchase application software: 1 week (during the system design documenta-

tion)

8 Core

1.2 Social and ethical designThis section builds on the social and ethical issues discussed in the Preliminarycourse. It examines the issues related to the implementation of a new system.

Design of systemsInformation systems should be designed to take into account the strengths andweaknesses of both people and machines. People are good at understanding andthinking up new ideas but have an unpredictable memory and get bored with verystructured tasks. On the other hand, machines are good at repetitive tasks involv-ing endurance, consistency and speed. They have very predictable storage andretrieval times and can only perform structured tasks. The information processesin a system should exploit the strengths and avoid the weaknesses of people and machines. Machine-centred systems and human-centred systems provideexamples of contrasting designs.

Machine-centred systems are designed to simplify what the computer must do at the expense of participants. They assume people will follow confusingprocedures and illogical user manuals. If errors occur in a machine-centred system,they are usually blamed on the participant (operator error) rather than on thetechnology. Machine-centred systems are not always the best systems forparticipants.

Human-centred systems are those that make participants’ work as effectiveand satisfying as possible. They allow people to do their work without wastingtime and effort struggling with the information technology.

In the past, information systems were difficult to use. People needed to under-stand a programming language to complete the simplest tasks. Today, with devel-opments in technology such as graphical user interfaces, computers are muchmore user-friendly.

User-friendly describes a tool that people find easy to use. User-friendlyinformation systems are more productive as participants do not waste time andeffort dealing with the system. In other words, the information system does not

– Code and test the custom software: 5 weeks (after the system designdocumentation)

– Write hardware specifications: 1 week (after the system design documentation)– Obtain quotations for hardware: 2 weeks (after hardware specifications)– Select supplier of hardware: 1 week– Deliver hardware: 2 weeks– Install hardware: 1 week– Set up software: 2 weeks (after hardware is installed).

Draw a Gantt chart for the project. What is the minimum time for completion ofthe project?

6 A systems analyst has estimated the following time for these tasks: – Define and code input screens: 5 days– Define and code output screens: 3 days– Define data structure: 2 days– Define file structure: 4 days.

Draw a Gantt chart for the project if the tasks do not overlap. What is theminimum time for completion of the project?

Project work 9

get in the way of the work. The software in the information system is a criticalfactor in designing a user-friendly information system. It is the link betweenpeople and the machines. User-friendly software has the following characteristics:• prompts the user in non-technical terms (see Figure 1.5)• doesn’t require precise spelling of commands• uses a similar appearance and structure for multiple applications• provides easier ways of achieving a task, such as templates• structures menus so they are logical and easy to understand• adjusts software to the ability of the user so that, for example, beginners see

and use only basic features• allows previous work to be imported and used easily.

Figure 1.5 Wizards are a user-friendly feature.

Work environmentThe design of a system impacts on the work environment. The impact can bepositive or negative. That is, for some people a new system can be exciting andenjoyable while for others it is frustrating and difficult. When designing a newsystem, it is important to consider the health and safety issues and the nature of the work.

Health and safetyThe relationship between people and their work environment is called ergo-nomics. It refers to the process of designing or arranging workplaces, products andsystems so that they fit the people who use them. The way information tech-nology is used in the work environment can have an effect on the body. Incorrectuse of computers can cause health problems, such as eyestrain, headaches,backaches, fatigue, muscle pain and repetitive strain injury (RSI). To reduce thesehealth problems, numerous reports and standards have been developed that dealwith ergonomics and information technology. The recommendations are brieflyoutlined below:• Furniture. Furniture needs to be adjusted to suit each person’s body. The desk

and chair should be positioned to reduce strain and undue fatigue. Desk heightmust be between 660 mm and 680 mm. Chairs should have an adjustable seatheight that ranges from 370 to 520 mm. The seat should be flat, well paddedand slanted slightly backwards.

10 Core

• Information technology. The screen should be about an arm’s length away withthe user looking down on the screen. The keyboard must be detachable andpositioned so that the user’s forearms are parallel to the floor.The mouse mustfit the hand and be easily moved. Software must be ergonomically designed tomake the user feel relaxed and comfortable. It should minimise movement,improve speed and be easy to use.

• Environmental factors. Lighting needs to be uniform and bright enough for all text to be easily read. The air temperature should range between 20°C and 23°C. The relative humidity of the air should be between 30% and 70%with air movements less than 0.2 m/s. Noise levels should not exceed 55 decibels.

IITT FFaaccttIT FactThe most frequently reported health concern for information technologyparticipants is vision-related problems. Eye specialists estimate that 36% ofthese problems are related to the work environment.

Nature of workA new information system will change a participant’s work. It will be positive ifthe new system involves a variety of tasks and a balance between work and rest.However, if the new system creates high levels of stress, the impact will benegative. Stress may result from increased workload, inadequate job design, lack ofsocial relations or concerns about job security. New systems have an impact onwork in the following areas:• Use of skills. Participants may be required to retrain and learn new skills

(become multiskilled) or perform work requiring less skills (become deskilled).• Meaningful work. Participants who work on the computer may not understand

the importance of their work. Their work may be abstract in nature andfocused on symbols on the screen.

• Nature of the workplace. Part-time work and the use of contracted labour mayincrease. There is the expectation that workers will continually change jobsthroughout their careers.

• Social relationships. Social interaction may change when a new system isimplemented. For example, people looking at a screen for most of the day tendto have less social interaction.

Systems and ethicsEthics is a set of beliefs we hold about what is right and wrong. There are anumber of issues involving the use of information systems that many people areconcerned about. These include environmental damage, equity and access,invasion of privacy, freedom of information, computer crime and copyright.Theseissues will be discussed throughout the text.

EnvironmentInformation systems give us the power to affect the environment. They have theability to help us reduce pollution. The use of communication systems has thepotential to reduce the need for transportation and hence air pollution. It allowspeople to work from home, regardless of where they live. Communication systems

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also enable people to access electronic services in country areas. This may reducethe need for high-density housing and the overpopulation of cities.

Conversely, information systems are also increasing the damage to our environ-ment. The manufacture of silicon chips increases the consumption of fossil fuels,builds mountains of waste and produces toxic chemicals. Paper consumption byour printers is destroying our forests and increasing our consumption of fossilfuels. However, our reliance on paper as a medium is decreasing. Compact discs(CDs) are replacing such books as encyclopedias, and people are reading elec-tronic newspapers and magazines (see Figure 1.6)

Figure 1.6 Electronic newspapers.

EquityEquity concerns equal rights for all. It means that all people should have equal accessto the benefits of information technology. Information technology has the potentialto give many people equal access to education, employment, medical treatment andmany other benefits. It can overcome differences in race, sex, location or disability.Communication systems can give people in isolated communities the chance to gaineducation that was previously only available in larger cities. New technologies haveallowed people affected by disabilities to better participate in society, gainemployment and have greater freedom. On the other hand, people do not alwayshave equal access to information technology. People may be disadvantaged becauseof the cost of buying and training in the use of the technology.

Gender equity is a concern to many people. They argue that women are nottaking advantage of information technology in the same numbers as men.Significantly fewer women than men have information technology careers.Similarly, fewer women than men use the Internet regularly. There are severalreasons for this. There is an image in society that computers are ‘technical’ andtherefore an area more for men than for women. This image is reinforced byadvertising in the media that has traditionally targeted men and excluded women.

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Conversely, it can be argued that the percentages of men and women working ininformation technology are roughly the same as in any other industry. The factthat women are employed in the lowest paid positions, such as data entryoperators, has nothing to do with information technology. Gender equity is anissue throughout our society. For instance, the number of male doctors is muchgreater than the number of female doctors. Furthermore, there are many examplesof women playing a leadership role in information technology.

1 Outline the strengths and weaknesses of people and machines.

2 What are the differences between a machine-centred and a human-centredsystem?

3 What is the advantage of a user-friendly information system?

4 What health problems are caused by the incorrect use of computers?

5 Describe the ergonomic recommendations for furniture.

6 What are the environmental factors that affect the work environment?

7 How can a new system create a high level of stress?

8 Describe the impact of new systems on work.

9 How can information systems reduce pollution?

10 Why is gender equity a concern to many people?

LEARNING ACTIVITIES

1 ‘The use of information systems is impacting on our environment.’ Discuss thisstatement. Outline your view on this issue.

2 Choose a small business that uses an information system. List the advantages anddisadvantages the use of information technology may have on this business.Outline some of the issues raised by the use of an information system.

3 ‘Information technology has brought nothing but stress, suffering and deskillinginto modern society.’ Outline your view on this statement.

4 Imagine you are the project leader responsible for the development of a newsystem for a large organisation. Describe some of the steps you would take toreduce any social and ethical problems that might arise from its implementation.

5 The introduction of information systems has led to employment redundancy.Name and discuss two other social and ethical issues that are commonly associatedwith information systems.

1.3 Understanding the problemUnderstanding the problem is the first stage in the system development cycle.Theexact nature of the problem must be determined and whether it can be solved byan information system (see Figure 1.7). This may involve redefining the problemand identifying its important elements. A clear problem statement is essential atthis stage. Understanding the problem often involves a preliminary investigationand completing a requirement report. These concepts are briefly outlined here asthey were examined in detail in the Preliminary course.

Exercise 1.2

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Preliminary investigationA preliminary investigation, or requirement definition, determines whether aquick fix of the existing system will solve the problem or a new system isnecessary. The fundamental operations of and problems with the existing systemmust be understood. Each of the information processes is examined, and anydeficiencies in the existing system are recorded. The preliminary investigationtakes into account the needs and concerns of all the participants. Participants playan important part in developing a workable system.Their views are gathered usingdifferent data collection methods, such as interviews, surveys, observations andmeasurements. Data is collected to understand the problem and to develop anappropriate solution. Data collection is very important. If the data is incorrect, thenew system may not meet the needs of the participants.

Understandingthe

problem

Input• Problem• Participants• Data

Output• Clear problem statement• Requirements

Ι Ο

Figure 1.7 Block diagram of understanding the problem.

IITT FFaaccttIT FactIt is estimated that participants use only 30% of the software developed fora new system in the specified manner. The main reason for this statistic isthat developers do not understand what their participants need.

The requirement report is a statement about the need for a new system.It outlines the aims and objectives of the new system and how it will help theorganisation. The requirement report is based on data collected from the partici-pants. It must match the goals of the organisation to ensure that management issatisfied with the solution. The requirement report also provides an overview ofthe new system in terms of the data/information, information processes andinformation technology to be used. The requirement report is used to developpotential solutions to the problem.

PrototypesA prototype is a working model of an information system. Prototypes are built inorder to understand the requirements of the system.They also can help in definingthe problem to be solved and in determining how an information system mightsolve the problem. Prototypes can be used to test possible information systemfeatures. In this case, participants actively use the prototype to identify both goodand bad features of the new system. Prototypes may contain data entry screens anda small sample database or may use formulas that provide approximate results.

14 Core

A prototype assumes that the participants cannot say exactly what theproposed information system should do. It proceeds by building a succession ofmodels.The process is repetitive.That is, the participants evaluate the model, theysuggest improvements, and then another version of the prototype is built. Thesethree steps are repeated until the prototype successfully solves the problem or theproject is abandoned. Clearly, the later versions of a prototype are more detailedand accurate. When the prototype has clarified the requirements of the system, itis either discarded or adapted for more permanent use.

There are three main advantages in using a prototype:• The requirements of the system more accurately reflect the needs of the

participants. Most participants will better understand the new system if theyuse a prototype rather than read the design specifications.

• Participants have the opportunity to be involved earlier and more directly inthe development of the new system. This may reduce the number of changesrequired by the participants in the testing, evaluating and maintaining stage.

• The new system is easier to create from a prototype. For example, if a databasemanagement system (DBMS) was used to create a prototype, then some or allof the forms and reports developed for the prototype could be used to buildthe new system.However, using a prototype has some disadvantages. First, the greater involve-

ment of the participants could impact on their work with the old system. Second,the repetitive process of the prototype can be frustrating if the succeeding versionsdo not provide a better solution. Finally, successful prototypes can producesoftware that is difficult to maintain, unreliable or inadequate. This may occur ifany design restrictions are not taken into account when creating the prototype.

1 What is essential in the understanding the problem stage?

2 Describe some of the activities completed in the preliminary investigation.

3 What is provided by the requirement report?

4 Why are prototypes built?

5 What do prototypes contain?

6 Why is the use of a prototype a repetitive process?

7 Describe three advantages in using a prototype.

8 How could a greater involvement of participants in the use of a prototype be adisadvantage?

LEARNING ACTIVITIES

1 Explain why it is important to involve the participant in the system developmentcycle.

2 The first two stages of the system development cycle involve much consultationwith participants. However, participants usually do not have design or program-ming skills. Why does the project leader rely on information gathered fromparticipants?

3 Your family would like to create a yearly newsletter that contains the majorachievements of each family member. Create a prototype of the newsletter using

Exercise 1.3

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1.4 Making decisionsThis stage involves making decisions using the data gathered in the preliminaryinvestigation (see Figure 1.8). The first task is to develop one or more potentialsolutions to the problem. A computer system should be seen only as a tool thatmay offer the best solution to the problem. It is not the solution to every problem.Each potential solution is developed using the requirement report and the scopeof the problem. The scope of the problem places constraints on the new system.A constraint is a factor that affects the system and prevents it from achieving the desired objectives. There are different types of constraints, such as financial,technical, environmental or personal. For example, a financial constraint would bethe amount of money an organisation is prepared to spend to solve the problem.

After establishing several potential solutions, the project leader seeks furtherguidance from the management of the organisation. Management receives a brief written or verbal statement outlining the advantages and disadvantages of eachsolution. If the potential solutions seem appropriate, a feasibility study is carried out.

a software application. Discuss the model with your family and make any modi-fications. Save the prototype with the filename FAMILY.

4 A teacher at one school requires the students to summarise all the conceptspresented in this course, so a glossary is to be developed. The glossary consists ofkey terms, an explanation, text reference and relevant topic. Create a prototypefor this project using a DBMS. The prototype is to contain sample screens andreports. It should also contain sample data. Save the prototype with the filenameGLOSSARY.

Makingdecisions

Input• Problem statement• Constraints• Feasibility• Data

Output• Recommendation• SpecificationsΙ Ο

Figure 1.8 Block diagram of making decisions.

Feasibility studyA feasibility study is a short report that analyses potential solutions in terms ofthe known constraints and makes a recommendation. It does not attempt to finda detailed solution. The feasibility study briefly examines the available options,estimates costs and identifies any constraints to be considered. It judges whethera potential solution can actually be implemented. It should identify the nature ofany problems, indicating the size or magnitude of the problem and whether itappears to be solvable.The study also needs to indicate the scope or boundaries seton the development of a new system, such as the maximum cost or the amountof change that is acceptable. Feasibility studies are an extension of the preliminaryinvestigation and are divided into different sections (see Table 1.1).

16 Core

The initial sections of the feasibility study (problem definition, requirementreport and summary of investigation) state the nature of the problem, list the aimsand objectives of the new system and give an overview of the existing system.They identify problems or requirements that are not satisfied by the existingsystem and outline the constraints on the development of a new system.They alsorestate the aims and objectives of the new system more precisely than therequirement report.

The middle section of the feasibility study analyses the data collected in thepreliminary investigation. It often requires more data to be gathered about eachpotential solution.After analysing the data, each solution is briefly described withits expected advantages and disadvantages.These descriptions are written in termsof how well they meet the aims and objectives of the new system.

The result of the feasibility study is the recommendation. The recommenda-tion is based on a number of criteria, such as economic, technical, schedule andorganisational:• Economic feasibility compares the costs of developing the new system with the

expected benefits. A financial analyst is often asked to assess economicfeasibility. Economic feasibility is also called cost/benefit feasibility.

• Technical feasibility determines the information technology requirements ofthe new system and the technical demands that will be placed on the newsystem.

• Schedule feasibility determines whether time is available to implement thenew system.

• Organisational feasibility determines whether the new system will fit into theorganisation and meet the current goals and objectives. It also determineswhether the new system will have enough support from participants to besuccessfully implemented and whether participants can operate the system.A feasibility study has three recommendation options (no change, develop a

new system or investigate other solutions), and it often examines the effect ofadopting each of these recommendations.The managers of the organisation selectthe recommendation that seems most feasible. If the managers decide to proceedwith a new system, then a detailed analysis is completed.

The final section of the feasibility study is the project plan, which was dis-cussed earlier in this chapter.

Section ContentTitle page Project name, report title, authors, date

Contents A list of report sections and page numbers

Problem definition Exact nature of the problem

Requirement report Aims and objectives of the new system

Summary of investigation Overview of the existing system; benefits, costs andconstraints of the new system

Alternative solutions Expanded details of each proposed new system

Recommendations Recommended course of action; justify the decision

Project plan Schedule if the recommendation is to proceed

Appendix Supplementary material, such as surveys, Gantt chartsand diagrams

Table 1.1 Typical sections of a feasibility study.

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Analysis reportIf the managers decide to proceedwith a new system, then a moredetailed analysis is required. Theexisting system is investigated ingreater depth to ensure all currentoperations and problems areunderstood. The project leadermust also further clarify the needsof the new system (see Figure 1.9).This requires more data to begathered, using interviews, surveys,observations and measurements.When the data is collected, it mustbe organised and analysed. It isnecessary to understand the flow ofdata through the system and howthe data is processed within thesystem. Various tools are used forthis purpose, and they are described in the next section.

When the detailed analysis is completed, an analysis report is written.It provides more detail than was presented in the feasibility study. The analysisreport provides a basis for further development. The details of the new system arepresented, along with recommendations for design, implementation and main-tenance. The analysis report contains design specifications for the next stage. Thesespecifications give the general hardware configuration of the new system and designsfor both input and output.The analysis report is the basis for a more detailed projectplan. Remember that the project plan must provide an overall schedule, the detailsof the subprojects, and a schedule for each subproject, as well as identify the people,information technology and data/information required by the system.

17

Figure 1.9 Project leader discussing the systemrequirements with a participant.

IITT FFaaccttIT FactOne third of all software projects fail. The major causes of failure are lack ofparticipant input, lack of managerial support and incomplete designspecifications.

1 Describe the second stage of the system development cycle.

2 What is a feasibility study?

3 Describe the initial sections of the feasibility study.

4 What is economic feasibility?

5 What is determined by organisational feasibility?

6 What are the options available to management after receiving a feasibility study?

7 Describe an analysis report.

8 What are some of the design specifications contained in the analysis report?

Exercise 1.4

18 Core

1.5 Designing solutionsDesigning a solution is the transformation of the specifications into appropriatehardware, software and information processes. It involves purchasing hardware,writing or purchasing software, and specifying information processes to make thesystem operational (see Figure 1.10). Systems analysts and programmers often usea top-down approach to designing a solution. It divides a large, complicatedproblem into a series of smaller, easier to solve problems.The smaller problems aresolved and brought together to solve the larger problem. In addition to informationsystems personnel developing a solution, it may be developed by a participant.

LEARNING ACTIVITIES

1 A new system requires a piece of application software to run on a network. How-ever, the software licence states that the software can only be used on a stand-alone personal computer. The project leader needs to make a recommendation inthe feasibility study. What options need to be investigated by the project leader?

2 Melissa would like a digital camera so she can include photographs on her Website. Analyse the current trends in digital cameras and prepare a list of possiblesolutions. Make a recommendation and justify your choice.

3 Terry requires a personal computer for less than $3000 to access the Internet.Analyse the current trends in the computer market and prepare a set of designspecifications for Terry. The specifications should give the general hardwareconfiguration of the new system and any software requirements.

4 A feasibility study is to be completed for an online tutorial system for your school:a List three groups of people who will be affected by the new system.b For each group, describe some of the possible effects on them.c Describe some of the factors that will affect the recommendation.

5 Write a feasibility study using the information in the answers to the abovequestion. It should contain the following sections: title page, contents, problemdefinition, requirement report, summary of investigation and a recommendation.

Designingsolutions

Input• Specifications

Output• Hardware• Software• Information processes

Ι Ο

Figure 1.10 Block diagram of designing solutions.

Participant developmentParticipant development occurs when people within the information systemdevelop the solution. Participants produce their own information system usingreadily available information technology (see Figure 1.11). Information systempersonnel do not develop the system. Software tools for participant developmentinclude general applications, such as spreadsheets and DBMS, and specificindustry applications, such as software developed for real estate and libraries.

Project work

Participant development is used when the project is not a basis for other projectsand reliability is not crucial. For example, a solution created and tested by a teamof programmers will probably be more reliable than one developed by a user whois creating his or her first solution using a simple spreadsheet.

19

Figure 1.11 Software tools available on the Internet.

Participant development became a solution because information system per-sonnel were often very busy and unable to provide immediate service. Participantscould solve small problems using application packages and allow the informationsystem personnel to focus on the major problems. The stages in the systemdevelopment cycle are affected by participant development:• Understanding the problem—participant identifies the problem. Information

system personnel might be used to advise the participant on possible tools tosolve the problem.

• Making decisions—participant chooses an appropriate solution.• Designing solutions—participant develops the solution, often using guided

processes found in application packages. The participant may require sometraining to design a solution.

• Implementation—participant begins using the system. This stage is often easierto accomplish with participant development than with a system developed byinformation system personnel as the participant is familiar with the applicationand does not require further training.There is no issue regarding acceptance ofthe solution by the participant.

• Testing, evaluating and maintaining—participant is totally responsible for themaintenance and testing of the solution and determining if any changes needto be made to the solution.Participant development is more responsive to participant needs and has the

potential to save time and money. It reduces the involvement of information systempersonnel.There is no need for programmers. In addition, the participant does nothave to communicate his or her needs during the initial stages, and training in theimplementation stage should be reduced. However, there are some disadvantages:

20

• Participants who develop a solution are not hardware experts. Informationsystem personnel often make more informed decisions and may receive adiscount for bulk purchases. They also have specialised knowledge about theparticular equipment that they purchase.

• Applications and the operating system chosen by a participant may be differentto those used by other participants in the organisation. This creates additionalcosts in terms of site licences and training. Incompatible software makes itdifficult for people to work together.

• Participants need access to data for their solutions. This creates securityproblems. Downloading data to a disk and transferring it to another computerincreases the risk of the data being stolen.Participant development could also be a component of the system develop-

ment cycle. First, the core of the information system is created by the informationsystem personnel based on the design specifications. Second, the participantsdevelop the user reports and screens using a fourth-generation language (4GL)that can be taught to users. This approach maintains control of the system whileproviding some of the advantages of participant development.

Design toolsDesign tools assist in the development of a new system. They describe theinformation processes and rules within the system. Design tools include contextdiagrams, data flow diagrams, system flowcharts, decision trees, decision tables anddata dictionaries.

Context diagramsA context diagram is a graphical method of representing a system that uses onlya single process together with inputs and outputs (external entities). There areonly three symbols in a context diagram: the process, data flow and external entity(see Table 1.2). The external entities are linked to the single process by data flowarrows. A context diagram is often the starting point of a data flow diagram(discussed below). The context diagram in Figure 1.12 shows a system forsearching the Internet. It clearly shows the flow of data in the system.

20 Core20

Symbol MeaningSingle process: A circle is used to represent the entiresystem.

Data flow: An arrow is used to represent the flow of data between the process and external entities.

External entity: A square or rectangle represents anyperson or organisation that sends data to or receivesdata from the system.

Table 1.2 Symbols used in a context diagram.

Process

Externalentity

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Data flow diagramsA data flow diagram (DFD) is a graphical method of representing a system thatuses a number of processes together with inputs, outputs and storage. A DFDfocuses on the flow of data between information processes in a system. It showswhere data is collected, organised, analysed, stored, processed, transmitted anddisplayed. DFDs provide a simple technique for visualising the movement of dataand describing what participants do rather than what the computers do.There arefour main symbols in a DFD: the process, data flow, data store and external entity(see Table 1.3).

Symbol MeaningProcess: A circle is used to represent the processes oractions that transform inputs to outputs.

Data flow: An arrow is used to represent the flow of data between the process, external entity and data store.

Data store: An open rectangle represents the locationwhere data is stored. It could be a filing cabinet, harddisk or DVD.

External entity: A square or rectangle represents anyperson or organisation that sends data to or receivesdata from the system.

Process

Externalentity

Data store

Table 1.3 Symbols used in a data flow diagram.

The data flows and data stores are given names to describe the data. Theprocesses should contain a description of the change in data. Each process mustcontain at least one input and at least one output. The DFD in Figure 1.13illustrates the movement of data for searching the Internet. To draw a DFD, startwith the processes and link them to data stores and external entities using dataflows. It is often easier to start with a simple diagram, such as a context diagram,and then add some more details. If the DFD becomes too complicated, it shouldbe broken down into a smaller DFDs. This creates different levels. The top-levelDFD identifies the major processes while lower-level DFDs add the detail.

Figure 1.12 Context diagram for searching the Internet.

Usesearchengine

StudentKeywords Internet address

Student

22222222

Decision trees and decision tablesThe information processes that operate on data in most information systems aredetermined by decisions.These decisions are made on the basis of the data enteredinto the system according to a set of rules or conditions. Two tools used to displayand analyse decisions are decision trees and decision tables.

A decision tree is a diagrammatic way of representing all possible combinationsof decisions and their resulting actions. It represents the decisions made within asystem as the branches of a tree. Each branch ends with a particular action. Thedecision tree in Figure 1.14 shows decisions made when searching the Internet.It is applying rules based on the number of hits.

22 Core

Usesearchengine

StudentKeyword

Keyword Graphic

Internet address

Internetaddress

Databaseof

Web sitesProject

LoadWeb site

Figure 1.13 DFD for searching the Internet.

Number of Websites is lessthan 10

Search

Condition

Number of Websites is greaterthan 10

No result

Action

Use a morespecific search

Try a new keyword

Access each Website

Figure 1.14 A decision tree for searching the Internet.

DFDs and context diagrams are easy to understand as there are only three orfour symbols. Participants can see what tasks are completed by the informationsystem. Context diagrams and DFDs often identify issues of responsibility beforethe system is designed. However, the simplicity of these design tools createscertain limitations. For example, they do not show the sequence of operations ordecisions that are needed by a programmer.

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Data dictionaryA data dictionary describes the data within the system. It is a tool used to managethe information resources. A data dictionary is often used to assist the design andcheck the accuracy of data flow diagrams. It is also a starting point for designingscreens and reports. (See Figure 1.16.)

✘ ✘ ✓

✓ ✘ ✘

✘ ✓ ✘

✓ ✘ ✘

✘ ✓ ✘

✘ ✘ ✓

Number of Web sites is greater than 10Number of Web sites is greater than 10

Number of Web sites is less than 10

No results

Use a more specific search

Access each Web site

Try a new keyword

Conditions

Actions

Rules

Figure 1.15 A decision table for searching the Internet.

Data item Description ExampleWeb site Domain name of Web site www.hi.com.au Internet address Unique address 205.188.200.58 Author Name of author Bloggs, Joe Start Date created (dd/mm/yy) 02/12/99 Keyword List of keywords technology, computer

Figure 1.16 A data dictionary of Web sites.

A data dictionary also describes each field in the database. It providesinformation about the characteristics of each item entered in the database, such asthe field names, field sizes, data types and field descriptions. Data dictionaries maycontain validation rules that specify appropriate codes, ranges or values for eachdata item. For example, a validation rule for a data item named State might onlyallow participants to enter one particular abbreviation for each state name, suchas NSW for New South Wales or QLD for Queensland.

A decision table is a table that represents all possible conditions and actions.It indicates the alternatives for different conditions and actions based on the rules.The table is divided vertically into conditions and actions, and then horizontallyinto rules. The decision table in Figure 1.15 shows the decisions made whensearching the Internet. Decision tables are often more difficult to understand thandecision trees, especially when decisions are based on previous decisions.

24242424

System flowchartsA system flowchart is a graphical method of representing both the flow of dataand the logic of a system. It documents the essential details of the system, such asthe sequence, the processes, and the precise rules for selecting particular actions.A system flowchart also shows the hardware used to process data, such as theperipheral devices, storage mediums and processing units.

System flowcharts use standard flowcharting symbols plus special symbols forperipheral devices (see Table 1.4). Some of these symbols have become out ofdate, such as the punch card symbol. Each symbol contains messages and is linkedby lines called flowlines.

24 Core

Symbol Meaning Symbol Meaning

Input/output Manual operation

Paper document Magnetic tape

Online display Direct accessstorage device

Online input Flowline

Punched card Telecommunicationslink

Process Predefined process

Terminal Decision

Table 1.4 Symbols used in a system flowchart.

The system flowchart in Figure 1.17 clearly illustrates the logic of a system for finding information on the Internet. It shows the sequence, selection andrepetition involved in the system.

Project work 25

1 Describe the third stage in the system development cycle.2 What is participant development?3 How are the stages in the system development cycle affected by participant

development?4 Describe three disadvantages of participant development.5 Name and describe the three symbols of a context diagram.6 What is a data flow diagram?7 Name and describe the four symbols of a data flow diagram.8 What is the difference between a decision tree and a decision table?9 Describe some of the information provided by a data dictionary for a database.

10 What is a system flowchart?

Exercise 1.5

Figure 1.17 System flowchart for finding information on the Internet.

Begin

End

Project

Internet browser

Access search engine

Enter keywords

Search results

Access a Web site

Read data

Is dataappropriate?

Are youfinished?

False

False

True

True

26 Core

Implementing

Input• Solution• Training• Conversion• Testing

Output• Using new system

Ι Ο

Figure 1.18 Block diagram of implementing.

LEARNING ACTIVITIES

1 Why is it important to consider how data is manipulated by a system in the systemdevelopment cycle?

2 A study system is a process to improve HSC results. Students decide the subjects tobe studied and the amount of time required. The study system produces theknowledge and understanding needed for the HSC examination. Construct acontext diagram for the study system.

3 The study system in question 2 is extended to include a table and a tutor. The tablelists the subjects and time allocations. Construct a data flow diagram to show thestudy system.

4 The table in question 3 is created using a word processor by following theseprocesses: enter subjects and time, save data, format table, edit table if required,print table. Construct a system flowchart for the study system.

5 An organisation intends to pay a bonus to some of its employees. To be eligible forthe bonus, an employee must have worked for the organisation for at least twoyears. Managers get $700 and other employees get $500. Construct a decision treeand a decision table to clarify this process.

6 Al’s Mechanical Repairs has developed a policy for accepting a customer’s cheque.The cheques will be accepted if all of the following conditions apply: cheques areless than $300, current driver’s licence is shown, and customer’s signature matchesdriver’s licence signature. Construct a decision tree and a decision table to clarifythis process.

7 A shoe store offers a discount on the number of shoes purchased by the customer.If customers buy one pair of shoes, they receive no discount; two or three pairs ofshoes, they receive a discount of 10%; and more than three pairs of shoes, adiscount of 15%. In addition, if their purchases are greater than three pairs ofshoes and exceed $200, they receive a further discount of 5% (for a total discountof 20%). Construct a decision tree and a decision table to clarify this process.

1.6 ImplementingThe implementation stage delivers the new system to the participants. It involvesusing the solution to solve the problem (see Figure 1.18). The implementationstage may involve a major change in the way the organisation operates. To ensurethe new system is successfully implemented, it must be carefully planned.Implementation procedures need to be carried out in the correct order. Forexample, it is necessary to ensure the hardware of a system is installed before thesoftware is set up. Large projects require an implementation plan to detail theparticipant training, the conversion method and the system testing.

Project work 27

Participant trainingTraining ensures participants can use the new system and understand its benefits.Training is also needed in the installation of a new system and to ensure that thecomputer is being used efficiently. The type of training depends on the existingknowledge of the participants and the features of the new system.

Training is provided by range of different people and technology (see Figure1.19). Management may decide to train one person who has responsibility fortraining other people. The suppliers of the hardware and software may carry outsome training. Training specialists instruct participants in how to operate theirsystem. Training manuals and pre-sentations are used to explain thenew system and any changes in theinformation processes.

Initial training is completedbefore the old system is convertedto the new system. Participantsmay also need training updates tokeep pace with the latest develop-ments in hardware and software.

Technical support staff arepeople who assist participants of asystem on an as-needed basis.Theirservices are usually provided overthe phone. Technical support staffneed to be completely familiarwith the system.

Conversion methodThe method of conversion is the way in which the information processesperformed by the old system will be transferred to a new system. It must becarefully planned and executed to avoid errors.The method chosen for conversiondepends on the nature of the work and the characteristics of the new system.There are four methods of conversion: direct, parallel, phased and pilot.

Direct conversion involves the immediate change to the new system on achosen date. On that date, the old system ends and the new system starts. All datafrom the old system is transferred to the new system, and the participants stopusing the old system and begin using the new system. Direct conversion is notcommonly used even though there are minimal transition costs. One reason thatdirect conversion is not commonly used is that it does not allow the project teamto check whether the new system will operate correctly and whether participantsunderstand the system.Another reason is that, if the new system fails or problemsoccur, the old system is not available as a backup.

Parallel conversion involves the old and new systems both working together atthe same time. Participants can compare both systems and obtain a goodunderstanding of the differences between the systems. If there are any problemswith the new system, it can be solved before the old system is discontinued.However, parallel conversion results in additional workloads for participants asthey must operate both systems until the new system is accepted. It may alsoresult in confusion about which system has the correct data.

Phased conversion involves the gradual implementation of the new system.Certain operations of the new system are implemented while the remainingoperations are completed by the old system. When one operation of the new

Figure 1.19 Multimedia used for training.

28 Core

Pilot conversion involves trialing the new system in a small portion of theorganisation. The old system is still available if the new system fails or experiencesproblems. Pilot conversion is usually started by a keen group of participants whoappreciate the benefits of the new system. If pilot conversion works, it is usually easierto motivate the other participants of the organisation to change to the new system.

System testingTesting a system is a very important part of theimplementation of a system. Without rigoroustesting, the system cannot be guaranteed to work asexpected. Tests must be designed to examine thesystem operation under all possible events. It isnecessary to test both the information technologyand the information processes:• Hardware is tested using diagnostic software and

through general operation (for example, thespeed and resolution of a printer). Backupsystems should be tested by selecting files to berestored (see Figure 1.21).

• Software is tested using data that has beenstructured to test all decisions made within the system. This test data mustcover all possible combinations of data that may be encountered. It should bebased on the original design specifications.

• Information processes are continually tested during the implementation of thesystem over a period of time. Minor changes to procedures are immediatelyimplemented.

Old system New system

New system

Old system

New system

Old system Old system

Old system

New systemOld system

New system

Figure 1.20 Methods of conversion.

Figure 1.21 Magnetic tapeused for backup.

system is successful, another operation is implemented until the new system isfully operational. Each operation is individually tested. If there is a problem witha certain operation, it is possible to switch back to the old system. Unfortunately,phased conversion is often confusing because some participants are on the oldsystem and some are on the new system.

Name Method of conversion over timeDirect conversion

Parallel conversion

Phased conversion

Pilot conversion

Project work 29

1.7 Testing,evaluating and maintainingAfter the new system is fully implemented, participants expect the system to beworking correctly. The successful operation of a system involves the informationtechnology working correctly and the participants using it effectively. Peopleresponsible for operation of the system include computer operators and managers.

1 Describe the fourth stage of the system development cycle.

2 List the contents of an implementation plan for a large project.

3 Why is participant training necessary?

4 Describe some of the training provided by training specialists.

5 List the four methods of conversion.

6 What are the risks of implementing a new system using direct conversion?

7 Explain the difference between parallel conversion and phased conversion.

8 Why is testing a system very important?

9 What is test data?

LEARNING ACTIVITIES

1 Write an outline of a training program to help beginners use the Internet. The training program should include accessing Web sites, using domain names andusing search engines. The training program must specify a list of appropriate Web sites.

2 What is the method of conversion in which a new computer system is developedand implemented alongside the old system until the new system is working well?Outline the advantages and disadvantages of this system.

3 A project leader is preparing to meet management and participants to discuss themethod of conversion to a new system. At this meeting, the project leader wishesto discuss two alternative conversion strategies. Compare and contrast twomethods of conversion that could be proposed by the project leader.

4 A school is implementing an electronic attendance system. This will replace themanual method of checking students’ attendance. Initially, the new system will beused to check the attendance of one group of students. The number of groups willbe gradually increased until the system is fully implemented. What is the methodof conversion to the new system? Do you think it is the best method of conversionfor this project? Why?

Exercise 1.6

Testing,evaluating and

maintaining

Input• Using new system

Output• Modifications• Upgrade

Ι Ο

Figure 1.22 Block diagram of testing, evaluating and maintaining.

30 Core

Computer operators perform tasks onthe equipment, such as monitoringperformance, starting up, running jobs andbacking up. The operators manual is usedto specify tasks to be completed on aregular basis. If there are problems and thesystem breaks down, the problems must bediagnosed and corrected immediately. Thecomputer operator attempts to identifythe problem and, if necessary, liaises with atechnician to rectify the problem.

Managers are responsible for theeffective use of the system. They overseethe computer operation and ensure thatparticipants and machines work efficiently

(see Figure 1.23). There are many different types of managers with slightly differ-ent roles. An information systems manager plans and oversees all the informationresources in the organisation.

After the new system has been in operation for a number of months, it must betested and evaluated.

Testing and evaluatingIn this stage, the performance of the system is tested and then evaluated. Testinga solution ensures that it works. Testing is carried out throughout the systemdevelopment cycle. Evaluation determines whether the system is working asexpected or whether changes are required. It occurs after the new system isestablished and minor problems have been fixed. The project leader, in consulta-tion with participants, often completes an evaluation. It is based on interviews,surveys, observations and measurements. During an evaluation, the results of thenew system are compared to the initial aims and objectives outlined in therequirement report.

Evaluation is ongoing. If the new system is not performing, then changes needto be made. If a major upgrade is required, then the system development cyclestarts again. The results of the evaluation are the basis for understanding theproblem in the next cycle. Information systems are involved in a constant processof evaluation, analysis and development to improve their efficiency. Evaluation isalso used to improve the processes involved in the system development cycle. Insome situations, evaluation results in the system undergoing maintenance.

Figure 1.23 Managers of a system.

IITT FFaaccttIT FactMicrosoft builds software products by first identifying the new capabilitiesthat customers request and then identifying any features it wants to includefor its own strategic reasons.

MaintenanceMaintenance is the modification of the system by making minor improvements.During the operation of the system, participants may discover deficiencies in thesystem and suggest improvements. For example, a secretary may suggest somechange in the format of an input screen. Maintenance may also involve installing

Project work 31

new hardware and upgrading softwarepackages. The longer the system hasbeen operational, the more difficult it isto change. However, good documen-tation makes it easier to undertakemaintenance without causing problemselsewhere. Simple changes in a largeinformation system are often complex toimplement and require retesting of otherparts of the system. This often results instarting the system development cycleagain. The tasks in this stage are ongoingand continue until another system isdeveloped or the system is terminated.

Operation manualAn operation manual details procedures participants follow when using a newsystem. Participants need to be instructed about and assisted with the majorfeatures and functions of the system.To create an operation manual, it is necessaryto determine the background of the participants. This will determine the format,language and depth of instructions required. A beginner will need simpleinstructions using non-technical language and may need additional guidance, suchas tutorials. The operation manual is usually presented as a hard copy, althoughonline versions are frequently available. Some of the factors for creating an easy-to-use operation manual include:• user-friendly format and structure• clear and concise instructions• steps listed in point form• tasks completed in the simplest way• appropriate instructions for file management and security• screen dumps included where possible.

Case study

Port Nelson Tourism is a small, privatelyowned business that works with the localcommunity to promote the region’s touristattractions. It produces printed material to advertise tourist attractions, such asbeaches, fun parks, sporting activities andcruises. The promotional material is dis-tributed at tourist information booths,motels, tourist attractions and shoppingcentres. Port Nelson Tourism receivesincome by charging businesses for inclusionin their printed material and by sellingadvertising space.

Port Nelson Tourism would like toexpand their business by developing arestaurant guide. This guide would beaimed at both tourists and local residents.To develop a solution, the manager of PortNelson Tourism completed the systemdevelopment cycle:• Understanding the problem—a meet-

ing was arranged with the owners ofthe major restaurants in the region. Thisprovided general directions about thepossible formats and typical informa-tion to be included. Then a survey was

Port Nelson Tourism

32 Core

sent out to all restaurants, and this datawas analysed to determine the require-ment report.

• Making decisions—a feasibility studywas completed that recommended a40-page booklet be published for thesummer season and that two additionalstaff be contracted for the project. Aproject plan was then developed toschedule subprojects, such as datacollection and graphics. The analysisreport outlined specifications for therequired information technology and amore detailed costing. A process ofchecking was to be implemented tovalidate the data.

• Designing solutions—a data flow diagram was used to specify the infor-mation processes and the flow of data. Each restaurant was visited, theemployees were interviewed, and photographs were taken. A high-performance personal computer and adigital camera were purchased alongwith a word processing program,painting program and desktop pub-lishing program. A template for the

publication was created to ensureconsistency. Ergonomic furniture waspurchased in consultation with the staff.

• Implementing—staff were given somebrief training with the new system, asthey were experienced users. The book-let was created in a desktop publishingprogram by importing the text from aword processing program and thegraphics from a painting program. Eachrestaurant was given a draft copy of thebooklet before publication.

• Testing, evaluating and maintaining—the new system was monitoredthroughout the implementation stage,and changes to the front page designwere suggested. At the end of thesummer season, a series of interviewswere completed to evaluate the per-formance of the finished product. Thefeedback was positive; however, somechanges to the structure of the bookletwere suggested. The manager of PortNelson Tourism evaluated the projectand recommended a second edition bepublished next year.

1 Describe the final stage of the system development cycle.2 What does the computer operator do if the system breaks down?3 Describe the role of a manager.4 What is testing?5 How is a new system evaluated?6 List two tasks that may be performed during maintenance.7 What is an operation manual?8 Describe some of the factors for creating an easy-to-use operation manual.

LEARNING ACTIVITIES1 Why should a new system be evaluated after installation?2 If a system is designed correctly, it should carry out the required tasks. Why is there

a need for ongoing testing and evaluation?3 A desktop publishing program was part of the solution in the case study.

Investigate the latest desktop publishing software. Suggest the most appropriatepackages for this situation. Justify your answer.

4 A high-performance personal computer was mentioned in the case study. Describea high-performance personal computer. List any peripheral devices that would berequired by Port Nelson Tourism to implement its new system. Investigate theoptions and costs of each device. List these details.

5 Interviews were part of the evaluation in the case study. Which people should beinterviewed? Make a list of interview questions that could be used to evaluate therestaurant guide.

Exercise 1.7

Chapter review

Project work 33Project work 33Project work 33Project work 33Project work 33Project work 33

PART A

Select the alternative (A, B, C or D) thatbest answers the question.

1 A diagram where the vertical axis liststhe tasks and the horizontal axis showsthe time frame is called a:A decision tableB Gantt chartC system flowchartD data flow diagram

2 A system designed to make partici-pants’ work as effective and as satisfy-ing as possible is called:A equity systemB human-centred systemC participant systemD ethical system

3 The third stage in the development of anew system is:A understanding the problemB implementingC making decisionsD designing solutions

4 During the development of a project,the details of the time schedule occur inthe:A feasibility studyB prototypeC project planD operation manual

5 In the feasibility study, the projectleader focuses on:A the appropriateness of a solutionB the cost of the new systemC designing a system to meet the

participants’ needsD how the existing system works

6 In a data flow diagram, a person whoreceives data would be represented by a:A external entityB data flowC processD online output

7 The conversion method where the oldand new systems both work together atthe same time is called:A pilotB directC parallelD phased

8 When a new system is not meeting theoriginal requirements of the problem, itis necessary to:A change the managementB retrain the participantsC restart the system development cycleD evaluate the system

9 In which stage of the system develop-ment cycle is a decision tree used?A testing, evaluating and maintainingB understanding the problem C implementing D designing solutions

10 The most likely location for the descrip-tion of data is a:A operation manualB data manualC data dictionaryD data validation

Chapter review

34 Core3434343434

PART B

For each of the following statements, selectfrom the list of terms the one that mostclosely fits the statement. Write the lettercorresponding to your choice next to thestatement number.

Statements

1 A table that represents all possibleconditions and actions.

2 The immediate change to the newsystem.

3 The process of planning, schedulingand controlling all the activities withineach stage of the system developmentcycle.

4 A series of stages used in the develop-ment of a new information system.

5 The general hardware configuration ofthe new system and designs for bothinput and output.

6 A short report that analyses potentialsolutions and makes a recommendation.

7 Determines if a quick fix of the existingsystem will solve the problem or a newsystem is necessary.

8 A working model of an informationsystem built in order to understand therequirements of the system.

9 When people within the informationsystem develop the solution.

10 A graphical method of representing asystem using a number of processestogether with inputs, outputs andstorage.

11 The gradual implementation of thenew system.

12 Details the procedures participantsfollow when using a new system.

List of termsa data flow diagramb decision table

c direct conversiond feasibility studye operation manualf participant developmentg phased conversionh preliminary investigationi project managementj prototypek specificationl system development cycle

PART C

Write at least one paragraph on each of thefollowing.

1 What is a Gantt chart? Draw a Ganttchart for the activities you completedtoday.

2 Briefly outline some of the ergonomicissues that impact on the design of anew system.

3 Why do people create a prototype?How are prototypes used to develop anew system?

4 Describe the typical sections of afeasibility study.

5 Explain the use of the following tools inthe design of a new system:a decision tableb data dictionary.

6 What are the reasons for participantdevelopment? Describe some of thetools used for participant development.

7 Pilot conversion is used in the imple-mentation stage of the system develop-ment cycle.a Explain the process of pilot con-

version.b What are the advantages and dis-

advantages of using pilot conversion?

8 Describe the final stage of the systemdevelopment cycle.

22IINNFFOORRMMAATTIIOONNSSYYSSTTEEMMSS AANNDDDDAATTAABBAASSEESS

cchhaapptteerr









Outcomes

The emphasis in this chapter is on the infor-mation processes of organising, storing andretrieving with database systems and hyper-media. You will gain a greater understanding ofinformation systems and develop skills withrelational databases.

Overview

36 Core

2.1 Information systemsIn the Preliminary course, you studied the basic concepts of an informationsystem. Information systems perform a set of information processes requiringparticipants, data/information and information technology. They perform theinformation processes of collecting, organising, analysing, storing/retrieving,processing, transmitting/receiving and displaying information. The relationshipbetween the elements of an information system is described in Figure 2.1. Thelinks between the elements are represented using arrows. Information systems arecreated for a purpose and operate in a particular environment.

INPUT

STORAGE

PROCESSING

OUTPUT

OUTPUTCONTROL

Figure 2.1 Information system.

Characteristics of information systemsInformation systems are created to provide access to information for an organisa-tion or individual. For a large number of information systems, the data is held in adatabase and access is achieved using a DBMS. The characteristics of an informa-tion system are the:• Organisation of data into information. Data must be organised before it can be

stored and analysed by the information system. Careful thought is needed toorganise data; otherwise, the resulting information will be meaningless.Organising may require sorting, summarising or classifying. Data in aninformation system is organised into data structures using such organisationalmethods as data dictionaries.

• Analysis of information to give knowledge. Access to information and theresulting knowledge is the purpose of an information system. For people togain knowledge from information, the information must be analysed.Information systems provide a range of tools for the analysis of data, such astables, queries and reports. People make decisions based on the informationthey receive from an information system.

Information systems and databases

Types and purposes of information systemsThe types of information systems and their purposes are changing with develop-ments in information technology. These types and purposes are also not mutuallyexclusive. They often overlap and change as new applications or new versions ofexisting applications are introduced.

Five types of information systems are examined in this section.Transaction processing systems (TPSs) collect, store, modify and retrieve the

daily transactions of an organisation. Some examples of the application of TPSsare buying goods at a point-of-sale (POS) terminal, processing credit card pay-ments and tracking receipts of materials from suppliers. Organisations rely heavilyon their TPS. A breakdown will disrupt operations or even stop the business. Forthis reason, well-design backup and recovery procedures are essential. There aretwo types of transaction processing: batch processing and real-time processing.Batch processing collects the transaction data into a group and processes it later.It is currently used where transaction data is on paper, such as processing cheques.Batch processing has a time delay, and this may be a significant disadvantage. Inreal-time processing, each transaction is immediately processed. It provides instantconfirmation of a transaction but does require access to an online database.

Decision support systems (DSSs) assist people to make decisions by providinginformation, models and analysis tools.A DSS can be used on a daily basis or whenan organisation has to react to something unexpected or make changes. Oneexample of a DSS is a system that analyses the stockmarket and helps the usermake decisions about buying and selling shares. A DSS creates a mathematicalmodel of the variables affecting the decision, using statistical tools, databases,spreadsheets and graphics. The model allows a manager to ask what-if questionsby changing one or more of the variables and seeing the projected results. Whatwould happen if the price were raised? What would happen if the organisationchanged the design of its package? The DSS depends on the accuracy of themathematical model and the ability of the manager to formulate appropriatequestions. Expert systems are a type of DSS.

Expert systems provide information and solve problems that would otherwiserequire a person experienced in that field (an expert). They are useful indiagnosing, monitoring, selecting, designing, predicting and training. An expertsystem asks users a set of questions and compares their answers to a knowledgebase. The knowledge base is a set of general facts and if-then rules supplied by anexpert. The expert system must reason to obtain a possible solution. For example,one expert system has been designed to help doctors diagnose infectious blooddiseases and prescribe antibiotics (see Figure 2.2). The system uses the patient’smedical history, symptoms and laboratory test results as its input and comparesthese to its knowledge base. If a match occurs, the system uses its pharmacologicalknowledge base to recommend an antibiotic.The solutions from an expert systemare not always correct, and it is up to the user to accept or reject the solution.

37

IITT FFaaccttIT FactA spider or crawler is a program that visits Web sites and reads their pagesto create entries for a search engine. It is called a spider because its ‘legs’ spana large area of the ‘Web’.

38 Core

Management information systems (MISs) provide information for theorganisation’s managers.An MIS presents basic facts about the performance of theorganisation. Some common examples of MIS output are reports on sales, stockinventory, payroll, orders and budgets. The fact that people are aware of how theperformance is measured helps managers motivate workers and make decisions.A special type of management information system is called the ExecutiveInformation System (EIS). The EIS is designed for the information needs of seniormanagers and provides information on strategic issues, using data from the sharemarket, commodity prices, interest rates and other economic indicators.

Office automation systems provide people with effective ways to completeadministrative tasks in an organisation. An office automation system uses a rangeof software tools, such as word processors, spreadsheets, databases, desktoppublishing, presentation programs and project management software. Officeautomation systems also use communications technology, such as Web browsers,email, facsimile, and video-conferencing. In office automation systems, letters anddocuments are constructed quickly, edited if required and easily stored for futurereference or re-use. Email improves productivity by delivering messages and datamore quickly than the paper-based interoffice mail system could. Desktoppublishing software is used to create high-quality flyers, reports and brochures.

Examples of database information systemsMost information systems store data in a database. Information systems that use adatabase are called database information systems. You will remember from thePreliminary course that a database is an organised collection of data. Databases areaccessed by a database management system (DBMS). A DBMS has no data in it.It is a software package that allows the user to enter, maintain and provide access

Figure 2.2 Expert systems are used in medicine.


to a database. The user can choose which data is required and how to display thatinformation in a meaningful way. The term database is often used instead ofDBMS.

There are many examples of database information systems, such as schooldatabases that hold information on teachers, subjects, classrooms and students.This chapter will use the Address and School databases to explain the importantconcepts involved in a database information system. Two other examples ofdatabase information systems are the RTA holding information on automobilesand video stores holding information on borrowers and videos. These latter twoexamples are used in case studies in this chapter.

39

Case study

MovieTime Video is a store that uses adatabase information system. The store’spurpose is to hire videos and sell associatedproducts. The environment is not only thecontents of the store but such factors aslocation, communications, suppliers, com-petitors and borrowers. MovieTime uses a

POS system, and electronic funds transferat point of sale (EFTPOS) is available.MovieTime Video performs a set of infor-mation processes that requires partici-pants, data/information and informationtechnology (see Figure 2.3).

MovieTime Video

Purpose• Hire videos and sell associated products

ParticipantsData/Information

InformationTechnology

• Scan video/card

• Search database

• Save database

• Update data

• Transfer data

• Display information

• Manager

• Staff

• Member data

• Video data

• Barcodes

• Receipt

• Personal computer

• Barcode reader

• Database

Information Processes

Information System

Figure 2.3 Hiring a video at MovieTime.

40 Core

A database is used to store membershipdata, video data and all video transactions.When new customers come into the store,they fill out a membership form containingpersonal details. The membership dataconsists of their last name, first name,address, home phone number, date ofbirth, and work phone number. The data isentered into a membership table. Newcustomers select a personal identificationnumber (PIN) and receive a membershipcard with a barcode. When the store buysa new video, data is entered into the videotable. The video data consists of an identitynumber, title, main stars, rating, and anentertainment category. The videos arealso barcoded for efficient processing.When a customer borrows a video, themembership and video barcodes are bothscanned. This data is automatically insertedinto the membership and video tables (seeFigure 2.4).

The participants at MovieTime Videoare continually carrying out the informa-tion processes. These processes are notcompleted in any order. The staff can movefrom collecting the data to displaying theinformation. The information processesinclude:• collecting—scanning the video bar-code• organising—searching the database for

membership details• analysing—determining the type of

information required (see Figure 2.5)• storing and retrieving—saving the data-

base to a disk• processing—updating the data after it

has been entered• transmitting and receiving—transfer-

ring the data between peripheraldevices

• displaying—obtaining a report on amember’s transactions (see Figure 2.6).

MovieTimeVideo

Member

Card, PIN, cash

Video, receipt

Transactiondata

Member dataVideo data

Videodatabase

Figure 2.4 Flow of data at MovieTime Video.

Information systems and databases 41

Figure 2.6 The results of the query in Figure 2.5.

Figure 2.5 Constructing a query for MovieTime Video.

1 What is an information system?

2 List five types of information systems.

3 Explain the difference between batch processing and real-time processing.

4 What factors is a DSS dependent on?

5 Where are expert systems useful?

6 What is the knowledge base in an expert system?

7 What information is presented by an MIS?

8 Describe an office automation system.

9 The following questions relate to the MovieTime Video case study:a What is the purpose of MovieTime Video?b Describe the participants, data/information and information technology.c List the data in the membership table.d List the data in the video table.e Describe the information processes at MovieTime Video.

LEARNING ACTIVITIES

1 Information systems are making unprecedented changes to our society. Brieflydescribe the effect of information systems on your way of life. Then select oneimpact of an information system that you regard as the most significant. Give areason for your choice.

Exercise 2.1

42 Core42 Core

2.2 Organisation methodsOrganising is the process of arranging, representing and formatting data.It involves the concept of a database. A database is an organised collection of data. People have used this concept of a database throughout the existence of thehuman race.

Non-computer and computer-based methodsPeople need to keep information about themselves and their activities. Commondatabases in the home include telephone books, dictionaries, recipe files, encyclo-pedias or even a list of things to be done. A database is simply a place to organise

and store data so that it can beretrieved later for a particular pur-pose. A telephone book is a non-computer database that organisesdata alphabetically according to aperson’s family name. Searchingfor the person’s name retrievestheir phone number. A paper filing system is a non-computerdatabase. It involves paper, foldersand filing cabinets to store data inan organised way (see Figure 2.7).Searching the folders in the filingcabinet retrieves a single piece ofpaper.

Non-computer databases areoften the best way to organise data.It is convenient to obtain infor-mation from a book or access itfrom a filing cabinet. People caneasily and inexpensively organisedata using a non-computer data-

2 ‘New office automation systems do not always result in increased productivity.Workers often spend too much time on relatively unimportant tasks, such asreformatting documents, organising irrelevant data or surfing the Web.’ Do youagree with these statements? Why? What steps should be taken by the managerto ensure office automation systems are used productively?

3 Developing an effective expert system requires a large database and powerfulsoftware. Constructing the knowledge base is expensive and requires humanexperts who are willing to provide the data in a suitable form. Consider theseissues and then outline some areas where expert systems could be used effectively.Are there any areas where expert systems should not be used?

4 Construct a data flow diagram to describe the flow of data in an existinginformation system. Choose an information system that you use regularly.

5 In the MovieTime Video case study, the staff could store the history of the videosborrowed by a particular person as well as the address of that person. This datacould be valuable information to many other businesses, such as book companies.Outline the ethical issue raise by this situation. What is your view on this issue?

Figure 2.7 Non-computer databases have beenused for years.


base. They do not need a computer or computer skills. Non-computer databasesare easier to keep secure, and they remain more private. The data is more difficultto use for other purposes. For example, a telephone book does not allow a thief tosearch for an address and find the phone number of a house.

Computer-based databases are being increasingly used to organise and storedata. Some examples include taxation records, library systems, car registrations,student records, CD-ROM encyclopedias and census data. Computer-baseddatabases have several advantages over non-computer databases:• Easily edited. Data can be corrected and updated without having to retype all

the data.• Large storage. Data is stored on a disk and retrieved when required.• Fast retrieval. Data is searched and sorted quickly and accurately to obtain the

required information.• Display options. Data is presented in a variety of ways, using tables, forms and

reports to suit most purposes.Computer-based methods of organising include flat file systems, database

management systems and hypermedia.

Flat file databasesA flat file database organises data into a single table and is suitable for many smallapplications. Flat file databases organise data using data structures called files,records, fields, and characters (see Figure 2.8):• A file is a block of data. When you have done some work on the computer, it

is stored in a file. The Address database is a file. A file in a database is dividedinto a set of related records.

• A record is a collection of facts about one specific entry in a database. In theAddress database, a record is information about a person’s name, address andhome phone. A record is divided into one or more related fields.

• A field is a specific category of data in a database. In the Address database, thefamily name, given name, street, suburb, postcode and home phone are fields.Data items in a field are made up of characters.

• A character is the smallest unit of data that people can use. Characters includeletters, numbers, and special symbols.

Figure 2.8 Part of the Address database.

Keys are fields that are used to sort and retrieve information. Usually, each keyholds a unique item that applies to only one record.When the records are sorted, thekey is used so that not all the data has to be read or retrieved. There are differenttypes of keys, such as a single key, composite key, primary key and secondary key:

Record

Field

Character

44 Core44 Core

• A single key is a field in which each item of data is unique. Care must be takenwhen choosing a single key, as some fields, such as Family Name, are not alwaysunique.

• A composite key, or compound key, is made by joining two or more fieldstogether. It is used when no data item in any field can be guaranteed to beunique. For example, a compound key can be made from such fields as Genderand Date of Birth.

• A primary key is a single key or compound key that must have a value. Primarykeys cannot be empty or null.

• A secondary key is a field that contains useful items of data often used insearches. Unlike other keys, secondary keys are not always unique.

Relational databasesA relational database organises data using a series of related tables. Relationshipsare built between the tables to provide a flexible way of manipulating and com-bining data. Forms are used to view, enter and change data in the tables. Relationaldatabases are the most commonly used database structure. The organisation ofdata in a relational database involves a schema.

SchemaA schema (pronounced ‘skee-ma’) is the data definition for a database. It is anorganised plan of the entire database showing how and where the data is found,descriptions of the data, and the data’s logical relationships. In a relationaldatabase, the schema defines the entities, attributes and relationships:• An entity is a specific thing about which information is collected and stored.

The School database has an entity for students, for teachers, for classes and forstudents and classes (see Table 2.1). A flat file database would have a separatefile for each of these entities.

• An attribute is a defined property of an entity. The Students entity in theSchool database has such attributes as LastName, FirstName andPhoneNumber. Each attribute of the entity contains a data item. Attributes arethe same as fields in a flat file database.

• A relationship is the way the entities are related to each other. In the Schooldatabase, the entities are related using keys, such as StudentID. Entities arerelated in three ways (see Figure 2.9):– A one-to-one relationship occurs when each record in the first entity is

related to exactly one record in the second entity. For example, in primaryschool each class has one teacher and each teacher relates to only one class.As another example, only one customer purchases a new car, and the sale ofeach new car is related to only one customer.

– A one-to-many relationship occurs when one record in the first entity isrelated to many records in the second entity, but any record in the secondentity only relates to one record in the first entity. For example, one studentcan take out many books from the library, but any one book can only betaken out by one student at a time.

– A many-to-many relationship occurs when each record in the first entity isrelated to many records in the second entity, and each record in the secondentity is related to many records in the first entity. For example, eachstudent studies many subjects, and each subject is studied by many students.


Entity AttributeStudents StudentID

FirstName

LastName

Address

Suburb

PostCode

PhoneNumber

Teachers TeacherID

Teacher

PhoneNumber

Extension

Classes ClassID

ClassName

TeacherID

Units

Students and Classes StudentClassID

ClassID

StudentID

Table 2.1 Entities and attributes for the Schooldatabase.

Figure 2.9 A relational database can use three types of relationships.

One-to-one

StudentStudent

Student

Student

One-to-many

Many-to-many

Physics Class IPT Class

Mathematics Class

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A foreign key is an attribute (field) of a table that is a primary key of anothertable. In the School database, the StudentID attribute is a foreign key of theStudents and Classes table and a primary key of the Students table. The data in aforeign key of one table must match the data in the primary key of another table.

TablesInformation about an entity is displayed in a table. A table is the organisation ofdata into columns and rows (see Figure 2.10). It is sometimes referred to as arelation. A column of a table is also an attribute of an entity or a field of a record.The data in a column must have the same data type and have a distinct name.A row in a table is also called a tuple of an entity, or one record. Each row mustbe uniquely identified by a key. The intersection of a row and column stores aparticular data item, such as ‘Rebecca’ in the first row and second column of theSchool database. The rows and columns in a table can be viewed in any orderwithout affecting the contents of the table.

Figure 2.10 Table from the School database.

FormsData is viewed for different purposes using forms. A form is used to view, enter,and change data in a table (see Figure 2.11). The layout of the form can bechanged. The user can position fields, headings, instructions and graphics. A well-designed form provides information explaining the required data and any data-entry rules that apply to particular fields. For example, the field name ‘Sex (M/F)’leaves no confusion about what data is required and how it should be entered.In a relational database, forms can be based on a single table or on multiple tables.

Figure 2.11 A form in the School database.

Tuple of theentity (record)

Attribute of the entity (field)

Key field


Data modellingData modelling is the process of identifying entities, the relationships betweenthose entities and the attributes of those entities. It is used to develop a schema forthe database. Data modelling is critical to creating an efficient database. There area number of tools used for data modelling, such as data dictionaries, schematicdiagrams and normalisation.

Data dictionariesA data dictionary is a comprehensive description of each field (attribute) in thedatabase. It contains information about the characteristics of each item entered inthe database, such as the field name, field size, data type and field description (seeFigure 2.12):• Field name is the name of the field. It should be carefully selected to avoid

confusion. Field names should be relatively short but clear and unambiguous.• Data type (or field type) is the kind of data that can be stored in the field. Each

field stores data in a single data type. Some common data types are text, memo,number, currency, yes/no and date/time. Logical fields contain the logic values‘true’ or ‘false’.

• Field size, or width, is the number of characters allowed in each field. It shouldbe limited to the smallest number of characters likely to be needed, as smallerfield sizes let the database work faster.

• Description specifies the contents of the field.

Figure 2.12 Data dictionary for the School database.

A data dictionary is a fundamental tool in the development of a database.It consists of metadata, or information about data. It provides a common groundfor people working on a project at the same time. For example, if people are

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working on different entities, they can refer to the data dictionary to checkwhether a particular attribute already exists. This reduces data redundancy. Dataredundancy is the undesirable duplication of data within a database.

Schematic diagramsSchematic diagrams are graphical tools that help define the database and developa schema. A common schematic diagram is called an entity-relationship diagram.

An entity-relationship diagram (ERD) is a graphical method of identifying theentities and showing the relationships between them. It helps to determine thedata to be included in and excluded from the database. ERDs force people to havea common understanding of the database. They are a useful tool to explain thedatabase. There are numerous notations for ERD. The ERD in Figure 2.13represents an entity as a rectangle and uses lines to specify the relationshipsbetween the entities.

Figure 2.13 An ERD generated from Microsoft Access for the School database.

NormalisationNormalisation is the process of organising data into tables so that the results ofusing the database are unambiguous and as intended. It is a refinement processthat aims to reduce data redundancy. Normalisation results in a database that ismore efficient but more complex because data is separated into more tables. Forexample, Table 2.2 is used to keep track of customer purchases and the price ofthe products. If you deleted a customer, you would also delete a price. Normalisingwould solve this problem by dividing this table into two tables: a table about eachcustomer and a product they had bought and a table about each product and itsprice. Making additions or deletions to either table would not affect the other.


The degree of normalisation has been defined in terms of forms, such as:• First Norm Form (1NF)—moving data items into separate tables where the

data in each table is a similar type. Each table is given a primary key. 1NF is thebasic level of normalisation and usually corresponds to the definition of adatabase.

• Domain/key normal form (DKNF)—a key uniquely identifies each row in atable. A domain is the set of permissible values for each attribute. Enforcingkey and domain restrictions ensures there are no problems when modifying thedatabase. DKNF is a final level of normalisation that most designers aim toachieve.

HypermediaHypermedia is a combination of media whose locations are linked electronicallyto provide an easy way to navigate between the information. The information isstored using a set of documents that may contain text, images, audio, video orexecutable programs. Each document is independent, and information is retrievedusing hypertext. Hypertext is a system that allows documents to be cross-linked insuch a way that the user can move from one document to another by clicking ona link. A link, or hyperlink, is indicated by a highlighted item (usually an under-lined word or a graphic) that allows the electronic connection. The author of thehypertext must specify the location of the information accessed by each link.If another computer is the destination of the link, that computer is called a node.The most well-known application of hypermedia and hypertext is the World WideWeb. On the Web, each document is accessed through its uniform resource locator(URL).

CustomerID Product purchased Price929 IT Today $50

970 Computers for dummies $45

568 Access made easy $60

Table 2.2 Customer table.

Uniform resource locatorA URL is the address of a file or resource on the Web. It is usually written in lowercase, as a single unbroken line, with no spaces (see Figure 2.14).The main parts ofthe URL are the:• protocol—the transfer method used to access a particular resource on the Web.

In most cases the protocol will be ‘http://’ (hypertext transfer protocol).• domain name—address of the specific computer where the resource is located,

such as ‘www.hi.com.au’. The domain name can be replaced by the IP address.

IITT FFaaccttIT FactThe Web is currently the largest index at over 200 million pages. Yahooemploys over 150 editors and Web surfers to create its directories.

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• file path—the full path to the file to be retrieved. It may be a simple filename,or it may be a directory path, such as ‘atlas/about.htm’. The domain name andthe file path are separated by a forward slash (/).

URLs must be complete and exact; if they are not, the file or resource will notbe found. It is not necessary to memorise URLs. Web browsers have the ability tostore the addresses of Web sites. These stored URLs are called bookmarks orfavourites and can be organised into categories or folders to save you time.

StoryboardA storyboard is a series of frames, each representing a different action or screenimage. It is a tool used to organise hypermedia. Storyboards are drawn on paper orusing a computer (see Figure 2.15). They are frequently edited. They define eachscreen and its specific media type. Storyboards consist of navigation paths,information and graphics.They are popular because they are simple to construct, areeasy to read and can be modified at every stage. There are four storyboard layouts:• linear—a simple sequential path that is set up quickly• hierarchical—a sequential path in a top-down design; the user starts at the

beginning and moves down through the multimedia product• non-linear—no structure; the user moves between different layouts in any

direction• combination—a blending of the above layouts.

Figure 2.14 A uniform resource locator.

/atlas/ This indicates a directorycalled ‘atlas’ within the Web site.

au This is a two-letter extension that indicates thecountry of the Web site (inthis case, Australia).Websites in the USA do not havea country extension.

hi.com This is known as the domainname. It is usually made up of the name ofthe organisation (hi for HeinemannInteractive) and an extension thatindicates the type of organisation (in thiscase ‘com’, which stands for ‘commercial’).

www This stands for theWorld Wide Web.

http:// This stands forhypertext transfer protocol,which is the set of rules thatgovern the transfer of data onthe World Wide Web. It indicatesthat the resource is a Web page.

http://www.hi.com.au/atlas/about.htm

about.htm This is the filename of an individual Web page in the subdirectory.The extension.htm stands for hypertext markuplanguage, which is the code usedto format all Web pages. SomeWeb pages have a four-letterextension (.html).


HTMLWeb pages are created using hypertext markup language (HTML). HTML is a setof special instructions that indicate how parts of a document will be displayed andnavigated. HTML documents are actually text files that contain HTMLinstructions. Many applications will save a document in HTML and insert thespecial instructions. HTML documents are viewed in a Web browser.

An HTML editor is a software program that specialises in writing HTML code.Instructions in HTML are given using HTML tags. HTML tags are metadata, orinformation about data. A tag consists of a left angle bracket (<), a tag name anda right angle bracket (>).Tags are usually paired, such as <H1> and </H1>, to startand end the tag instruction. The end tag looks like the start tag except a slash (/)precedes the text within the brackets. Every HTML document contains certainstandard tags, such as <head> and <body>. The <head> tag precedes the title andthe <body> tag indicates the beginning of the actual text (see Figure 2.16).

Figure 2.15 A storyboard layout.

Figure 2.16 A basic HTML document.

<html><head><TITLE> HTML </TITLE></head><body><H1>HTML document </H1><P>Welcome. This is a paragraph in HTML.It is just text!</P><P>This is another paragraph in HTML.HTML is easy.</P></body></html>

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Links are achieved using HTML’s hypertext-related tag. It is <A> and standsfor anchor. The document to be linked is specified using the instructionHREF=“filename”. The filename refers to the location, or path, of the link. Afterthe hypertext reference, the text that will provide the link is specified. Forexample, the format of a link is: <A HREF=“ipt.html”>technology</A>. Thehypertext reference is the document ‘ipt.html’, and the word ‘technology’ is the hypertext link to this document. If the hypertext reference is in a differentfolder or on another computer, its path must be specified. For example, the format of a link to the file ‘ipt.html’ on the ‘hi.com’ computer is:<A HREF=“http://www.hi.com/ipt.html/”>technology</A>.

1 What are the advantages of computer-based databases over non-computerdatabases?

2 Describe the data structure in a flat file database.

3 Explain the difference between a primary key and a secondary key.

4 What is a relational database?

5 Describe a schema.

6 List three ways entities are related.

7 What is data modelling?

8 What information is contained in a data dictionary?

9 What is the purpose of normalisation?

10 Explain the difference between a link and a node.

11 Describe the three parts of a URL.

12 What is a storyboard?

13 Describe HTML.

14 How are links achieved in HTML?

LEARNING ACTIVITIES

1 Investigate three different non-computer methods of organising data, such ascard files, filing cabinets and address books. How is the data organised? How isthe data stored? Who uses this method of organising data? Outline theadvantages and disadvantages of each method.

2 Find three different examples of non-computer databases in your home. For eachdatabase, answer the following questions:a What is the storage medium used for the data (what is the data stored in or

on)?b How is the data organised?c Is it possible to reorganise the stored data in a different way?d Is it possible to maintain the database by adding, deleting or changing the

information?

3 The library uses a relational database to store information about borrowers andbooks. Construct a schematic diagram to represent this existing system.

4 Stadium Australia has set up a booking system for all its events. The system uses arelational database. There are three entities: Customers, Seats, and Events.

Exercise 2.2


2.3 Storage and retrievalPeople need secure and efficient methods for storage and retrieval of informationfrom a database. The tool used for this purpose is called a database managementsystem.

Database management systemsA database management system (DBMS) is a software package that allows usersto access a database so they can enter, maintain and view the data. The termsdatabase and DBMS are often used incorrectly. A database contains the data, andthe DBMS provides access to this data. The data is independent from the DBMS.In a DBMS, data is organised into tables, viewed in forms, retrieved using queriesand displayed in reports. A DBMS manipulates the data in many different ways,such as sorting and searching. It also performs a number of tasks to help usersdevelop and maintain a database, such as:

– Customers: CustomerID, LastName, FirstName, Address, Suburb, PostCode,Deposit and CreditCard.

– Seats: SeatNumber, EventID and CustomerID.– Events: EventID, EventTitle, Date and Time.a What would be the primary key for each entity? Give a reason for your answer.b Create a data dictionary for this relational database. c Create a schematic diagram for this relational database.d Design a form for each entity that could be used for data entry.e The date of birth is a useful piece of information about the customer. Add this

attribute to the database.f Populate the database with dummy data. Save the database with the filename

STADIUM.

5 An organisation has a database that holds records of any gifts received from thecommunity during the year. The database is organised as follows:– Person: PersonID, LastName, FirstName, Address, AmountToDate, and

DateLastGift.– Gifts: PersonID, GiftDate and GiftAmounta What attribute in the database is redundant? Give a reason for your answer.b The manager of the organisation would like to personally thank all the people

who made a contribution to the organisation. He requires a list of supporters bystreet and suburb. Modify the data structure so that this information would beeasily obtained.

c What would be the primary key for each entity? d Create a data dictionary for this relational database. e Create a schematic diagram for this relational database.f Populate the database with dummy data. Save the database with the filename

GIFTS.

6 Max Music is a small business that offers an online ordering service for itscustomers via the Internet. It wants to expand its Web site by adding Web pagesto display the latest music releases. Each new Web page should containinformation about one CD, such as the artist, type of music, background, datereleased and a description. Construct a hypertext document from a storyboard forthese Web pages. Each Web page should be linked.

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• organising the data using a data dictionary• showing relationships between entities using schematic diagrams• checking for identifiable errors in data entry• allowing flexibility to change the definition of the database• restricting access to the data to authorised people (see Figure 2.17)• providing information about the performance of the database.

Methods of accessing dataSequential and direct access are two methods of accessing data.

Sequential access occurs when data is accessed in a sequence. It is the onlymethod of accessing data stored on magnetic tape. Data on a magnetic tape isretrieved by starting at the beginning of the tape and reading all of the data untilthe required item is found. Sequential access processes data in the order it wasstored. It does not require the exact location of the data item. Sequential access ismuch slower than direct access and impractical when immediate processing isrequired.

Direct access occurs when data is accessed without accessing previous dataitems. Data is stored in a particular storage location based on a mathematicalprocedure or algorithm. Direct access uses this algorithm to calculate theapproximate location of the data. If the data is not found at this location, thecomputer searches through successive locations until the desired data is accessed.Direct access often involves the use of an index and is then called indexed access.An index is a table that contains information about the location of the data. Datais accessed by referring to the index and obtaining the exact location of the data.Indexed access requires additional processing time to search the index and tomaintain the index. The indexed access method is widely used to store data on adisk, as well as to store the logical location of data within a database.

Distributed databasesA distributed database is a database located at more than one site. It acts as asingle collection of data but is geographically dispersed. Distributed databasesreduce the data transmission costs that would occur if all users at all sites had toaccess one centralised database. However, a distributed database makes it moredifficult to obtain a complete view of the database.

Distributed databases often need to be synchronised to keep them current.Consider a distributed database with part of the database at a warehouse and

Figure 2.17 Restricting access to a database.


another part at head office. If the office staff place an order from the warehouse,then both parts of the database need updating. This may create a problem if anerror occurs in transmission and only one part of the database processes thetransaction. A two-phase commit is part of the DBMS used to maintain con-sistency across a distributed database. It checks whether both parts of the databaseare ready for the transmission and then performs the transmission.

Storage mediaStorage of data is online or offline. Online storage uses a peripheral device that isunder the user’s direct control, such as a hard disk on a personal computer. Offlinestorage uses a peripheral device that is not under the user’s direct control, such asa centralised database. Both online and offline storage use a variety of peripheraldevices and storage mediums:• A hard disk is a disk made of metal or glass and covered with magnetic

material. Hard disks are usually mounted inside the computer’s case (fixed),and their storage capacity is usually measured in Gb. Magnetic disks use directaccess to retrieve data.

• An optical disc is a polycarbonate plastic disk with a reflective layer of metalcovering the surface. Data is read and written using laser technology. Opticaldiscs use direct access to retrieve data. There are many kinds of optical discs,such as compact disks with read-only memory (CD-ROMs) and digitalversatile disks (DVDs):– CD-ROM disks are 12 centimetres wide and capable of storing 650 Mb.

They are convenient for storing data that remains constant, such asencyclopedias.

– DVD is a disk format that can store large amounts of data. A DVD-ROM is the same physical size as a CD-ROM but provides storage of 4.7 Gb to 17 Gb.

• A removable cartridge is a hard disk encased in a metal or plastic cartridge andcan be removed like a floppy disk. Removable cartridges are fast, thoughusually not as fast as fixed hard disks, and use direct access. There are twocommon types of removable cartridges:– Zip disks (or cartridges) store 100 or 250 Mb of data and have a transfer rate

of 1 Mb per second.– Jaz disks (or cartridges) are an upgrade of the Zip disks. They store up to

2 Gb of data and have a transfer rate of 5.5 Mb per second.• A magnetic tape is a very long, thin strip of plastic, coated with a thin layer of

magnetic material.The tape is wound on two reels inside a cartridge. Magnetictapes can store large quantities of data inexpensively and are often used as abackup medium. They use sequential access to retrieve data.

EncryptionEncryption is the process of encoding data, and decryption is the process ofchanging it back (decoding). It is the most effective way to achieve data securityduring the transmission of data. Data is encoded, transmitted, and then convertedback to its original form. Encrypting data is essential for transferring financialtransactions and is used extensively on the Internet. Encryption methods ofteninvolve complex manipulations of bit patterns. One problem with encryption is tofind a method that is difficult to decode but is also practical to use. There are twomain types of encryption:

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• Asymmetric encryption requires a key for encryption and a key for decryption.A common asymmetric encryption system is public key encryption. It involvesa public key that is widely available and a private key that is kept secret. Bothkeys are developed using complicated number theory.The public key is used toencrypt the message before it is transmitted, and the private key is used todecrypt the message when it is received.

• Symmetric encryption requires the same key for both encryption anddecryption. A common symmetric encryption system is the Data EncryptionStandard (DES).

Backup and securityIf the computer goes down or the storage media or database is damaged, the costsof interrupted operations and replacing any lost data can be enormous. A DBMScontains backup and recovery capabilities to guard against data loss. A backup isanother copy of the data that can be used to rebuild the system. A DBMS createsa backup at a specified time. If the system goes down, the recovery processrebuilds the data. It uses the last completed backup and a journal listing all theactions completed by the DBMS since the last backup. The success of backup andrecovery depends on implementing appropriate procedures. Backups are usuallystored offsite or in a fireproof safe.

Security is another important databaseissue. Data can be stolen, destroyed ormaliciously modified. There is a greaterrisk when the data is accessible tomultiple users over a network. Datasecurity involves a series of safeguards toprotect the data. The first line of defenceis to only allow access to data byauthorised people using passwords,personal objects and biometric devices.However, some people are capable ofevading these procedures. Further safe-guards to protect data involve dataencryption and firewalls.A firewall can beused on the Internet or on any network toverify and authenticate all incoming data.It checks the password of anyone tryingto access the network. Firewalls areexpensive to install and maintain. Onlarge systems, more than one firewall isnecessary because barriers need to beplaced at all critical points.

IITT FFaaccttIT FactWhitfield Diffie and Martin Hellman invented public key cryptography in1976. For this reason, public key encryption is sometimes called Diffie-Hellman encryption.


SortingDatabase information is always easier to use when data is arranged in a meaningfulorder rather than randomly as it was entered. Sorting is the process of arrangingdata in a particular order. Sorts are performed in either ascending or descendingorder. Ascending order arranges data from smallest to largest (for example, 0 to 9)or from first to last (for example, A to Z). Descending order is the reverse, fromlargest to smallest (9 to 0) or from last to first (Z to A). Sorting can be done onmore than one field (attribute) so that records are arranged in the most usefulorder. For example, Figure 2.18 shows the School database sorted on two levels,with Last Name being the primary sort field and First Name the secondary sort field.

Figure 2.18 The School database sorted on two levels.

SearchingData needs to be quickly and efficiently retrieved from a database. Searching isthe process of examining the database to retrieve data. An effective search in asmall database may involve browsing a table or using the Find or Searchcommand. However, in a large database, the most efficient way of searching is toconstruct a query.

QueryingA query is a search of a database for records that meet a certain condition. It is aquestion you ask of the database. For example, what is the name of the studentwho lives at ‘4 Beach Rd’? The results of a query are usually displayed in a tablebut can be used as the basis of a form, report or graph or even another query. Aquery can also update or delete multiple records at the same time and performbuilt-in or custom calculations on data.

A query is constructed in the form: <Field name> <Operator> <data>. Thedata in the query is often called the criteria. For example, if the InformationProcesses and Technology class from the School database was required, the querywould be in the form ‘ClassName = Information Processes and Technology’. Acommon method for constructing a query is query by example (QBE). It requiresthe user to enter the criteria against a field. For example, in Figure 2.19, thecriteria ‘Information Processes and Technology’ is entered underneath theClassName field. If the search of a database involves two or more entities, it iscalled a relational query.

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OperatorsSome queries are constructed using anoperator, such as those in Table 2.3. Theoperator represents the action to beperformed in the query. Operators are classified as either relational or logical.

Relational operators (=, <>, <, >,<=, >=) are characters or symbolsindicating the relationship between twoexpressions. Wildcard characters representone or more unknown characters. Somecommon wildcard characters are theasterisk (*), which substitutes for anynumber of characters, and the questionmark (?), which substitutes for onecharacter. The query ‘LastName = Ma*’would find such last names as Mat, May,Madrid and Martinelli. However, the query‘LastName = Ma?’ would only find suchlast names as Mat and May.

Figure 2.19 A query by example on the School database.

Operator DescriptionRelational Operators

= Equal to

<> Not equal to

< Less than

> Greater than

<= Less than or equal to

>= Greater than or equal to

contains

does not contain

begins with

ends with

is blank

is not blank

Logical Operators

AND both

OR either one

NOT exact opposite

Table 2.3 Examples of operators.


Logical operators (AND, OR, NOT) are used to combine queries so that asearch is carried out on one or more fields. It is important to understand thedifference between the AND and OR operators:• The AND operator requires both the first and the second query to be true. It

retrieves records that satisfy both queries. For example, if you require dataabout a student with the last name Howe who lives in Kearns, the query wouldbe: ‘LastName = Howe’ AND ‘Suburb = Kearns’.

• The OR operator requires either the first or the second query to be true. Itretrieves records that satisfy either of the queries. For example, if you requiredata about all of the students with the last name Howe and all the studentswho live in Kearns, the query would be: ‘LastName = Howe‘ OR ‘Suburb =Kearns’.

SQLA query language is a specialised language designed to search a database. Thereare different query languages, each with its own grammar, syntax and vocabulary.Structured Query Language (SQL and pronounced ‘see-qwell’) is a querylanguage used to access and manipulate data in a relational database. Variations toSQL have been developed by specific DBMSs. However, most of these variationsare extensions to ANSI SQL, or standard SQL.

IITT FFaaccttIT FactSQL grew out of research on relational database models conducted by IBMin the 1970s. It developed from Structured English Query Language(SEQUEL). For this reason, the pronunciation of SQL is ‘sequel’ and not ‘squeal’.

SQL statements contain keywords that are used to perform a particular task.For example, the select statement is used to query the database and retrieveselected data that matches the criteria.A simple select statement may contain thekeywords SELECT, FROM, WHERE and ORDER BY (see Table 2.4).

Keyword Values Description Example

SELECT Field(s) The data to be displayed SELECT FirstName,LastName

FROM Table(s) The source of the data FROM Students

WHERE Search criteria The query WHERE LastName = “Mullins”

ORDER BY Field(s) The order in which the results ORDER BY LastName DESCare to be displayed

Table 2.4 Keywords used in a simple SQL select statement.

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When searching in SQL, it is essential to use the correct syntax. In mostDBMSs, the keywords are written in upper case, the fields are separated bycommas, an entity and an attribute in that entity are separated by a full stop, andthe search criteria or data item is enclosed in double quotes. The keywordORDER BY sorts on a field in ascending (ASC) or descending (DESC) order.Ascending order is the default and can be omitted. The SQL query in Figure 2.20is the same as the query in Figure 2.19 that was developed using QBE.

Figure 2.20 A SQL query on the School database.

Hypermedia and searchingData is retrieved from a database using the data structures and the relationshipsbetween entities. The process of retrieving data in hypermedia is completelydifferent. It involves using search engines.

Search enginesA search engine is a database of indexed Web sites that allows a keyword search.An index is a table that contains information about the location of data. A searchengine’s index is built by regularly scanning the Web for new sites and acceptingsubmissions from Web page authors.The scanning is often completed by programscalled spiders, crawlers or robots. They send back the URL of any document theyfind to the search engine’s indexing software (see Figure 2.21). This indexingsoftware collects information, such as titles and keywords, from the Web sites,then indexes these words in a database. Each search engine has a different methodof building its index; this is why you often obtain different results from the samekeyword search when you use a different search engine.

Indexes allow documents to be found using a keyword search. A keyword isentered related to the topic of interest. Most search engines allow a search on aseries of keywords and for specific information.When the user requests a keywordsearch, the search engine scans the index for the keywords and lists the Web sitesthat contain those keywords. Choosing the right keyword is crucial to the successof a search. In general, use more than one keyword such as synonyms and selectkeywords that are very specific. Search engines allow the use of Boolean qualifiers,such as ‘AND’, ‘OR’ and ‘NOT’ to refine a search.


Some search engines offer directories. Directories are lists of Web sitesorganised into categories, such as computers, games or sport (see Figure 2.22).They are another way to find information on the Internet. The owners of a Website have to register their site to be included in a directory. As a result, directoriescover only a small fraction of the pages available on the Web. A directory is usefulfor finding information on a general topic.

YOURCOMPUTER

URLsURLs

Keywords

WORLDWIDE WEB

SEARCHENGINE

Spiders follow hyperlinks on the World Wide Web

The spider sends back URLs to the search engine’s indexing software

You conduct a keyword search

A list of URLs for Web pages containing these keywords is returned to your computer

1

2

3

4

3

4

1

2

Database

Figure 2.21 How a search engine works.

Figure 2.22 Directories at AltaVista.

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A search robot is a program that accesses Web sites and gathers informationfor search engine indexes. AltaVista has a search robot called Scooter. It asks eachserver which files should be excluded from being indexed, it does not go throughfirewalls, and it uses a special algorithm so that response time for other users isnot affected.

1 Explain the difference between a database and a DBMS.2 Describe accessing data using an index.3 What is a distributed database?4 Briefly describe some of the storage media used by information systems.5 What is public key encryption?6 Describe the process of backup and recovery.7 Explain the difference between searching and sorting.8 What is QBE?9 List four keywords in SQL and describe their purpose.

10 How is a search engine index built?11 Describe a search engine that offers directories.12 What is a search robot?13 Write the meaning of the following queries:

a Class = 12*b Postcode = 261?c LastName begins with Hd Assessment > 60e FirstName = “Peter” AND Suburb = “Mossman”f Colour = “Red” AND Cost > $500g LastName = “Tran” OR PostCode = “2534”h StreetNumber = “9” OR Price < $500

14 Write out queries using relational operators for each of these searches:a Year 12 boys in the school.b Borrowers who live in either Auburn or Lidcombe.c Girls in the netball club who are eligible to play in 18 and under teams.d All customers who owe more than $10 000 for the month of July.

15 The following questions refer to the School database in Figure 2.18.a Write down the StudentID of the second record if sorted on ‘FirstName’ in

ascending order.b Write down the StudentID of the third record if sorted on ‘Phone Number’ in

descending order.c Which of the ‘Mullins’ would come first if the primary sort field was ‘LastName’

and a secondary sort field was ‘StudentID’?d Write down the StudentID of the first record if the primary sort field was

‘Address’ and a secondary sort field was ‘StudentID’?

Exercise 2.3


LEARNING ACTIVITIES1 Melissa Harris has decided to organise a small bus service. She has constructed a

database using the following data structure: – Bus: RegistrationNo, PeopleCapacity, Model, Colour and Details– Patron: PatronID, FirstName, LastName, Address, Suburb and Postcode– Job: JobNumber, PatronID, RegistrationNo, AmountReceived and Destination.Create a data dictionary and an ERD for this database. Populate this database withdummy data. Save the database with the filename SMALL BUS. Construct thefollowing queries:a All the buses with a capacity greater than 8 people.b All the buses whose model is a type of Toyota.c All the patrons whose last name starts with the letter ‘S’.d All the patrons whose address is in a street.e All the jobs where the amount received was greater than $40.f All the patrons where the amount received was less than $50.g All the jobs that used a Toyota bus or whose destination was Sydney.h All the patrons who travelled in a red bus and whose address contains the

letter ‘a’.2 A retail organisation keeps data about its employees in a database:

– Employee: EmployeeID, LastName, FirstName, Address, Suburb, PostCode, andDepartment

– Wage: EmployeeID, WeeklyPay, PayDate and WeeklyTaxa Describe the results of this SQL query:

SELECT FirstName, LastNameFROM Employee, WageWHERE Employee.Department = “Sport” AND Wage.WeeklyPay > 1000ORDER BY LastName

b Describe the results of this SQL query:SELECT EmployeeIDFROM Employee, WageWHERE Employee.Suburb = “Cabramatta” OR Wage.PayDate = #31/07/01#ORDER BY LastName DESC

c Construct a SQL query that could be used to retrieve the name of all employeeswho work in the office and live at either Ryde or Hunters Hill.

d Construct a SQL query that could be used to retrieve the name and address ofall employees whose weekly tax is less than $50 on 12 August 2001.

e Create a data dictionary and an ERD for this database. Populate this databasewith dummy data. Save the database with the filename RETAIL. Verify youranswers to the queries in questions (a) to (d).

3 The Internet has many large databases that can be accessed using a keywordsearch. Use your Web browser to access the following Web sites. Describe theinformation that can be obtained from each site.a http://www.whitepages.com.aub http://www.hoyts.com.auc http://www.tradingpost.com.au

4 Find information about databases on the Web by using more than one searchengine. Create a list of sites and their URLs that you found useful. Compare yourlist with another student in your class. Rank the top three sites from both lists.Compare these lists as a class. What are your class’s top three sites?

64 Core

2.4 Other information processesDisplaying is presenting the output from an information system or database tomeet a given purpose. The presentation of information could be in the form oftext, numerals, images, audio or video. A report is one way to display informationfrom a database.

ReportingA report is the formatted and organised presentation of data. Examples of reportsare mailing labels, invoices, sales summaries and telephone lists. A DBMS allowscomplete control in the design of a report in either a tabular layout (displays datawith the fields extending across the page) or a column layout (displays data withthe fields going down the page). It is possible to insert headings, sort data, choosethe fields, switch fields, change column widths and select records. The purpose ofthe report determines its content, format and style. Most DBMSs allow differentreports to be created from the database for different purposes (see Figure 2.23).

Figure 2.23 A report from the School database.

Before creating a report, the user needs to select the required records byconstructing a query. For example, you may not need a mailing label for everybodyin the School database. Reports are often based on a query. The next step increating a report is to select the fields. These fields are placed in appropriatepositions, formatted, and sorted. DBMS reports often offer such functions ascount, sum, and average to perform calculations on selected fields. Most DBMSreports have the following sections (see Figure 2.24):


• The report header appears once at the beginning of a report. It contains suchitems as a logo, report title and date.

• The page header displays information such as a title, column headings, or anyinformation needed at the top of every page. A page header appears after thereport header on the first page of the report.

• The details section displays most of the information. The user has a variety oftools to manipulate and format fields.

• The page footer displays information such as the date, page number or anyother information the user wants at the bottom of every page.

• The report footer appears once at the end of the report. It displays items suchas report totals.The report footer appears after the page footer on the last pageof the report.

Figure 2.24 Designing a report for the School database.

Constructing different viewsDifferent views of a database are obtained using a form. A form is used to view,enter, and change data in a table. The layout of the form can be changed. The user can position fields, headings, instructions and graphics on the form. A well-designed form provides information explaining the required data and anyrules that apply to particular fields. Forms are used to display information fordifferent purposes.

Before selecting the ‘Print’ command to send the report to the printer, makesure the report has the correct format. When formatting a report, the user needsto adopt good design principles, such as:• headings that identify the purpose of the report• layouts, such as tabular or column, that efficiently present the information• text that is balanced on the page either vertically or horizontally• styles that are consistent throughout the report and with its purpose• columns that have clear and descriptive headings• white space that is appropriately used to improve readability• page numbers and the date included in the header or footer.

66 Core66 Core

IITT FFaaccttIT FactStickiness is the quality of a Web site that induces visitors to remain on thesite rather than move to another site. It is the length of time a visitor accessesa site. Stickiness is a valuable measure for convincing advertisers topatronise a site.

Case study

The Roads and Traffic Authority (RTA) is an organisation that uses a databaseinformation system. Its purposes are toensure vehicles are safe and to provideindividuals with a driver’s licence. Theenvironment of the RTA is not only itsoffices throughout New South Wales butalso such factors as communications,insurance cover, police records and the costof new vehicles. The RTA performs a set of information processes that requiresparticipants, data/information and infor-mation technology (see Figure 2.25).

When the owner of a vehicle needs torenew the registration, he or she requires apink slip and a green slip. This data ispresented at one of the RTA offices. Acentral database is used to store the detailsof each vehicle, such as plate number,model and engine number. The owner paysthe registration and presents the pink andgreen slips. This data is automaticallyupdated using offline storage. An entityalso exists to store information aboutholders of driver’s licences, such as theirlicence number, address and expiry date.

Roads and Traffic Authority

Purpose• Ensure vehicles are safe

• Protect road users



• Collect pink/green slips

• Update database

• Search database

• Print details on rego form

• Manager

• IT personnel

• Staff

• Owner data

• Pink slip

• Green slip

• Terminals

• Central computer

• Database


Information System

Figure 2.25 Registering a vehicle at the RTA.


This information is also updated at RTAoffices. Information about registration ofvehicles and obtaining a driver’s licence is obtained from the RTA Web site (seeFigure 2.26).

The participants of the RTA are con-tinually carrying out the informationprocesses. These processes are not com-pleted in any order. The staff can movefrom collecting the data to displaying theinformation. The information processesinclude:• collecting—entering data from pink

and green slips

• organising—searching the database forowner details

• analysing—determining the type ofinformation required

• storing and retrieving—saving andbacking up the database

• processing—updating the informationin the database

• transmitting and receiving—trans-ferring the data between terminals andthe central computer

• displaying—printing details on theregistration form.

Figure 2.26 RTA’s Web site.

Figure 2.27 An ERD for the RTA, showing entities, attributes and relationships.

6868 Core

1 What is a report?

2 List some examples of reports.

3 Why is a report often based on a query?

4 List the sections of a report.

5 Explain the difference between a report header and a page header.

6 What is usually displayed in a report footer?

7 The following questions relate to the RTA case study:a What are the purposes of the RTA?b Describe the participants, data/information and information technology.c List the data in the registration table.d List the data in the driver’s licence table.e Describe the information processes at the RTA.

LEARNING ACTIVITIES

1 In the RTA case study, a relational database was used to organise and store data.Create a data dictionary and an ERD for this database. Populate this database withdummy data. Save the database with the filename RTA.a Create a report to display all the registration information. The report should be

sorted on expiry date in ascending order.b Create a report to display all the driver’s licence information. The report should

be sorted on expiry date in ascending order.

2 St Peters High School is using a relational database to store student data. Aportion of the database involves the following three entities: – Students: StudentID, FirstName, LastName, Address, Suburb, Postcode, Date of

Birth and Gender– Contact: StudentID, FirstName, LastName, Address, Suburb, Postcode,

MailingName and ContactPhone– School: StudentID, SportHouse and SubjectsCreate a data dictionary and ERD for this database. Populate this database withdummy data. Save the database with the filename ST PETERS. a Create a report that lists all the male students. The report should display the

students’ first name, last name and gender. It should be sorted on last name inascending order.

b Create a report that lists all the students who are in a particular sports house.The report should display the students’ first name, last name and contact phonenumber. It should be sorted on contact number in descending order.

c Write a letter using a word processor advising the contact person about someproposed changes to the school this year. Insert merged fields from thedatabase into the letter. Merge the letter and the database so that each personreceives a personalised letter. Create mailing labels for each letter, using thedatabase.

Exercise 2.4


2.5 Issues related to informationsystems and databasesBoth positive and negative impacts arise from the introduction of informationsystems and databases. In this section, we examine some of the social and ethicalissues raised by information systems.

Data sourceThe source of the data is the person or organisation that developed the data. Datamay come from informal sources, such as a conversation, meeting or observations.It may also be obtained from formal sources, such as a report, book or officialdocument. A formal source often provides data that is logically organised.However, this is no guarantee to its accuracy. The source of the data is protectedby the Copyright Act. People are not allowed to copy the work of another personwithout permission. It is against the law to violate copyright.

Most data obtained from the Internet is protected by copyright. Text andimages obtained from a Web site should not be used without acknowledgment ofand permission from the owner. However, the Copyright Act does make specialprovisions for students to use information for research purposes. It allows studentsto use a reasonable portion of the original work if the work is correctly cited. Tocite an Internet source, include the following information: author’s surname andinitial or organisation’s name, title of the complete work or Web page, URL of theWeb page, date of the document or Web page publication, and the download date.

Accuracy of dataAccuracy of data is the extent to which it is free from errors. Data that is collectedon individuals is not always accurate. The inaccuracies may be caused by mistakesin gathering or entering the data, by a mismatch of the data and the person, or byout-of-date information. For example, a car recorded as stolen is later recoveredand returned to the owner. If the data has not been quickly updated, the legalowner runs the risk of being arrested as a car thief. Opportunities to check andchange incorrect data need to be provided. It is often necessary to compare datafrom a number of different sources to determine which data is accurate.

Data validation is used to check the entry of data:• A range check is used if the data is restricted to a small range of particular

values. For example, when the data is entered in the format dd/mm/yyyy, arange check could be used to determine whether the first two digits are in therange of 1 to 31 and whether the second two digits are in the range of 1 to 12.

• A list check is used when the data can be compared to a set of accepted data.For example, when the data entered is an Australian state, then NSW wouldbe accepted but not NSX.

• A type check is used to determine whether the data type is correct (see Figure2.28). For example, when the data is entered for a person’s family name thesoftware will check whether the data is text. It would not accept a ‘date’ for aperson’s name.

• A check digit is a digit calculated from the digits of a code number and thenadded to that number as an extra digit. For example, the ISBN number 0 85859 921 319 4 has a check digit of 4, and the check digit is calculated from0 85859 921 319.

70 Core

Data integrity describes the reliability of the data. Reliable data is accurate,current and relevant. There is no guarantee that data received from the Internet isreliable. It is easy to publish information on the Internet. Organisations that arenot the creators of the information often provide access to it. Who is responsiblefor the accuracy of the information? Is the creator the only person responsible forthe accuracy of the data? Do organisations that provide access to information havea responsibility to verify its accuracy? Clearly it is necessary to compare data froma number of sources and to determine which data is accurate.

Figure 2.28 Data validation rules.

IITT FFaaccttIT FactA ghost site is a Web site that is no longer maintained but that remainsavailable for viewing. It is often difficult to identify ghost sites, as many Websites do not display the date of the last update.

PrivacyPrivacy is the ability of an individual to control personal data. It is a major concernfor those involved with databases and their use. Large organisations, such as banks,use databases to store information about their customers. This information isconfidential. It should not be used for other purposes or be made available toanyone outside the organisation. Privacy is also eroded by linking databases. Peopleleave a trail of electronic data when they use a credit card, visit the doctor, use thelibrary, access the Internet or subscribe to a magazine. If this data was combined,it could create a fairly detailed picture of a person.

Access to dataAccess to data is the extent data is available to people. Should all information befree and available to all? What kind of access should individuals have toinformation about themselves? Why can’t people have free access to data aboutthemselves located in business databases? Do people have the right to access andcheck their credit history or medical data? The Freedom of Information Act is

Invalid data type


designed to allow individuals to find out what data is being kept by thegovernment and other public bodies. It states that individuals have the right toaccess information where it relates to the individual and does not invade anotherperson’s privacy.There is a fee for the release of this information (see Figure 2.29).However, knowing what data is being kept does not indicate how it will be used.

Figure 2.29 Web site for Freedom of Information Act.

People can use our preferences, weaknesses and habits to their advantage. Thatis, data on what we buy, how we pay for it, what we read, what we watch ontelevision and how much we earn is valuable data for those who want to sell usthings. Ownership and control of this data is an ethical issue.Who owns this data?Is it the individual, or is it the organisation that has processed the data? Is the databeing combined, sold and exchanged? For example, an application for anextension to a house is sent to the local council for approval.Who owns this data?Does the building inspector have the right to sell this processed data to abricklayer? On the other hand, might the owner of the house appreciate anotherquote for laying bricks?

Data warehousing and data miningA data warehouse is a database that collects information from different datasources. It is a storage area of raw data that can be analysed to assist organisationsto make decisions.A data warehouse involves careful planning to decide what datato collect. The contents of a data warehouse are usually historical and static.However, they will change if new requirements are identified. A moresophisticated approach to obtaining information is to use data mining.

Data mining is a process that looks for relationships and patterns in the datastored in a database. It sorts through the data and turns up interesting and usefulconnections. For example, data mining could be used to analyse the transactions ata supermarket. It might determine that there was a relationship between tomatosauce sales and meat pie sales. This information might be useful for marketingpromotions. One problem with data mining is that many of the patterns occur bychance and have no value in making decisions. It also raises issues of privacy andownership of data.

72

Exercise 2.5

Core

1 Explain the difference between an informal and a formal source of data.

2 How do you cite an Internet source?

3 How is inaccurate data obtained?

4 List four methods of validating data.

5 Describe a range check.

6 Why is privacy a major concern?

7 What is the purpose of the Freedom of Information Act?

8 Describe a problem with data mining.

LEARNING ACTIVITIES

1 A flat file database is used by a school for student records. There are separate filesfor student data, financial data, teacher data and assessment results. A relationaldatabase has been suggested to the principal as a better system. Outline theadvantages of a relational database over a flat file database. Your answer shouldcontain references to data accuracy, data redundancy, security and developmenttime.

2 Privacy and access to data are two important issues related to databases. Considera student database containing name, address, gender, ethnicity, family, financialstatus, health, discipline record and assessment results. Should access to this databe given to the student, other students, teachers, the department of education,potential employers or other organisations? Is there a need to provide somegroups with limited access? Explain your answers.

3 ‘Databases should not have the same copyright protection as books and software.’Do you agree with this statement? Give reasons for your view.

4 Max Music is a small business that offers an online shopping service for itscustomers via the Internet. Customers place orders for CDs using their credit cardand register preferences for categories of music. This data is stored in a database.Research indicates that preferences for music are also a good indicator for bookand video preferences. Describe the ethical issues raised if Max Music sells eachcustomer’s preferences to a book company?


Chapter review


PART A


1 The main advantage of a computer-based database compared to a paperfiling system for retrieving informationis that the:A data can be searched more efficientlyB data is very accurateC storage medium is a hard diskD data is organised into data structures

2 What is the specific thing about whichinformation is collected and stored in arelational database?A fileB recordC entityD schema

3 A single key that must have a uniquevalue and is used to sort and retrieveinformation:A secondary keyB primary keyC composite keyD foreign key

4 A storyboard layout that has nostructure is called:A linearB hierarchicalC non-linearD combination

5 Metadata is contained in a:A data dictionaryB data recordC hyperlinkD primary key

6 A customer file contains an identifi-cation number that is linked to atransaction file. This is an example of a:

A hypertext linkB recordC keyD column.

7 The video staff wish to retrieve in-formation from the membership fileabout borrowers whose first name is‘Ann’ with a post code of ‘2176’ whoborrowed movies starring ‘Cary Grant’.A FirstName = “Ann” OR PostCode =

“2176” OR Mainstars = “Cary Grant”B FirstName = “Ann” AND PostCode =

“2176” OR Mainstars = “Cary Grant”C FirstName = “Ann” OR PostCode =

“2176” AND Mainstars = “Cary Grant”D FirstName = “Ann” AND PostCode =

“2176” AND Mainstars = “Cary Grant”

8 Metadata is used in the organisationand retrieval of data. One example ofmetadata is the:A records stored in a database.B tables used to organise data into

rows and columns.C HTML tags used to create Web pages.D search engines used to retrieve data

from the Web.

9 A query uses a wildcard to search adatabase in the form FirstName =“M?c*”. Which of the following wouldnot be retrieved?A MichaelB MickC MacD Mitchell

10 The reliability of the data in a databaseis called:A data securityB data redundancyC data integrityD data validation

74

Chapter reviewPART B


Statements

1 A database that organises data using aseries of related tables.

2 A query language used to access andmanipulate data in a relational data-base.

3 The address of a file or resource on theWeb.

4 Data accessed without accessing pre-vious data items.

5 The data definition for a database.

6 A field that is used to sort and retrieveinformation.

7 A comprehensive description of eachfield in the database.

8 A formatted and organised presen-tation of data.

9 A technique to reduce data redundancy.

10 A system that allows documents to becross-linked.

11 Data accessed in a sequence.

12 A search of a database that meets acertain condition.

List of terms

a data dictionary

b direct

c hypertext

d key

e normalisation

f query

g relational

h report

i schema

j sequential

k SQL

l URL

PART C

Write at least one paragraph on each of thefollowing questions.

1 What is hypermedia? How are docu-ments created on the Web?

2 Explain the difference between thefollowing terms:a schema and data dictionaryb data validation and data redundancy.

3 What is a DBMS? Outline some its func-tions.

4 Explain the difference in organisationalmethods between a flat file databaseand a relational database.

5 Describe a method of identifying enti-ties and showing their relationships.

6 Outline two methods for constructing aquery.

7 Describe the process of retrieving datausing a search engine.

8 Identify a social or ethical issue involvedin keeping data about individuals in adatabase. Briefly explain how the rightsof the individual can be protected inthis case.

74 Core

33CCOOMMMMUUNNIICCAATTIIOONNSSYYSSTTEEMMSS

cchhaapptteerr









Outcomes

This chapter features the information processesof transmitting and receiving using communi-cation systems. You will learn the characteristicsof communication systems and some of theirapplications. The chapter provides a compre-hensive understanding of networks and theissues related to communication systems.

Overview

76 Core

3.1 Characteristics ofcommunication systemsA communication system enables people to send and receive data andinformation. We depend on communication systems. The telephone, radio andtelevision are examples of communication systems that have had a dramaticimpact on our society. All communication systems have five basic components:1 The data source produces the data to be sent.2 The transmitter encodes the data into a signal suitable for a transmission

medium.3 The transmission medium is a channel, such as a cable, in which the signal is

transmitted to the destination. The signal may be changed or distorted duringtransmission.

4 The receiver decodes the signal back into the original data or an approximationof the data.

5 The destination is the receiver of the information.These components can be applied to any communication system, such as the

radio. In radio, the data source is the person speaking into the microphone. Thetransmitter is the microphone and associated electronics that change the sound intoa signal.The transmission medium, or channel, is the space between the transmittingand receiving antennas. The receiver is the radio that converts the signal into theoriginal sounds, and the destination is the person listening to the radio.

Communication systems are used in information systems when participantsneed to transmit and receive data and information.When people withdraw moneyfrom an ATM, they are accessing an information system and using a com-munication system (see Figure 3.1). Data and information are being transferredbetween an ATM terminal and the bank’s central computer. When computers and other devices are connected in some way like the ATMs, they form a net-work. In this topic, we are focused on communication systems that involve a network.

Good communication systems havean accurate, reliable and secure trans-mission medium. They should also havea minimum delay in communicating.Good communication depends on pro-tocols, handshaking, speed of trans-mission and error checking.These factorsdepend on the information technologyused in the communication system.

Figure 3.1 ATMs are part of a communicationsystem.

Communication systems

Protocols Communication systems need protocols for communication. A protocol is a set ofrules that governs the transfer of data between computers. It defines how theinformation is transmitted and how the errors are detected. Two computers mustuse the same protocols when they are communicating; otherwise, the data transfermay be unsuccessful. The standardisation of data communication protocols hasbeen the focus of a major international effort over many years. Protocols arewritten into internationally accepted standards, such as the OSI reference model.

The OSI reference model divides data communication into seven layers. Eachlayer expresses the standard, using a protocol.The bottom layers are responsible fortransfer of data from one place to another. They include protocols that specify thetype of plugs, the format of data, the method of transmission and error checking.The top layers examine the exchange of data between application programs. Theyinclude protocols that specify file transfer, passwords and network management.

HandshakingData can only be successfully transferred between devices if handshaking occurs.Handshaking is an agreement about which protocol to use to accomplish theexchange of information. It is a series of signals that flow between devices duringdata transmission. When using a modem, a handshake is those crunching soundsheard when making a connection. Handshaking is needed between devices as theymay have different capabilities and may transfer data in different ways.

Handshaking involves sending signals to indicate the type of protocol to beused. The transmitting device will send a signal and wait for an appropriateresponse. When two devices successfully handshake, then a connection is made.When a handshake is not successful, then the devices ‘hang up’ and try again.There are two methods of handshaking to control the flow of data:• Hardware flow control uses a dedicated connection, such as a wire. It is only

practical when devices are close enough to be linked with a cable. A commonhardware protocol is RTS/CTS (request to send/clear to send).

• Software flow control uses a special code sent with the data. It is used for longdistance communication. A common software protocol is XON/XOFF (Xstands for transmit). If a break in transmission is needed, then the XOFFcommand is sent.When transmission is to start again, then the XON commandis sent.

Speed of transmissionThe speed of data transmission isdetermined by the transmittingdevice and the bandwidth. Thebandwidth is the capacity of thechannel, or transmission medium. Atransmission medium with a highbandwidth can transfer more data.For example, a fibre-optic cable has ahigh bandwidth. When cabletelevision is transmitted throughfibre-optic cable, many differentchannels can be transmitted at the same time.

77

Figure 3.2 Modem speeds are measured in bitsper second.

78 Core

The speed of data transfer is measured by the number of bits per second or bythe baud rate:• Bits per second (bps) is the maximum number of bits that can be transmitted

in one second.This measure of speed includes special bits used in asynchronoustransmission and any error checking bits. Bps is also called the bit rate.

• Baud rate is the maximum number of data symbols or electrical signals thatcan be transmitted in one second. Because a data symbol can contain morethan one bit of data, the baud rate and the bit rate may be different. Forexample, 1200 baud might transmit at 4800 bps.

Error checkingWhen data arrives at its destination, it may contain errors. These errors may be caused by interference with the signal or simply by errors in encoding anddecoding the data. Errors must first be detected and then corrected. Threecommon methods for error detection are parity checking, checksum and cyclicredundancy check:• Parity checking is a method of checking for errors in data transmission using an

additional bit called a parity bit. This bit is used only for the purpose ofidentifying whether the bits being moved have arrived successfully.When datais represented using an 8-bit ASCII, then a ninth bit is used that holds a 0 or a1. When an odd parity is chosen, the number of ones in the nine bits must beodd. This means that if the number of ones in the first eight bits is even, thenthe parity bit must be one to make it odd. If the number of ones in the firsteight bits is odd, the parity bit must be zero to keep it odd. The sender andreceiver can also decide to send an even parity, in which case the number ofones in the nine bits must be even. If an error has occurred in a single bit, thenthe parity will be different and an error in transmission has occurred.

• Checksum is a method of checking for errors in data transmission by countingthe number of bits in a data packet. A data packet is created by dividing thetotal data into smaller groups.The count of the bits in a data packet is attachedto the data packet. It is used by the receiver to check whether all the bits havearrived successfully. If the count matches, it is assumed that a completetransmission was received.

• Cyclic redundancy check (CRC) is a method of checking for errors in datatransmission using a division process. The data is divided into predeterminedlengths and divided by a fixed divisor. The remainder of the calculation isattached and sent with the data. When the data is received, the remainder isrecalculated. If the remainders do not match, an error in transmission hasoccurred. There are a number of different standards for CRC. A 32-bit CRCachieves a 99.99% detection of all possible errors.

The most common form of error correction is to retransmit the data.

IITT FFaaccttIT FactA Web gardener is a person who acts like an editor to ensure thatinformation posted on a Web page is accurate and relevant.


Communication settingsThe characteristics of the communication system are the basis of the com-munication settings. Communication settings can be changed by the user toensure a connection between two devices. The settings are often a parameter. Aparameter is a variable that is given a constant value for a particular application.Some common parameters include bps, data bits, parity, stop/start bits and flowcontrol.• Bits per second is the speed of transmission, such as 56 000.• Data bits are the number of bits in each group of data. Each data group is

usually sent as a byte, such as 7-bit ASCII or an 8-bit ASCII.• Parity is whether the data contains a parity bit for error detection. Parity is odd,

even or none.• Stop/start bits are the number of stop and start bits used in asynchronous

transmission. This parameter is used to identify each byte. The normal range isbetween 0 and 2. Some systems only use a stop bit.

• Flow control is the software handshaking protocol, such as XON/XOFF.

79

Figure 3.3 Parameters for a modem.

80 Core

3.2 Examples of communicationsystemsNew communication capabilities have made it possible for people to do manythings that were not possible a few years ago. This section examines threeexamples of communication systems: teleconferencing, messaging systems andelectronic commerce.

1 Describe the five basic components of all communication systems.

2 Explain the difference between a protocol and handshaking.

3 What is the OSI reference model?

4 What is involved in the handshaking of two devices?

5 Describe software flow control as a method of handshaking.

6 What is the bandwidth?

7 Explain the difference between baud rate and bps.

8 Describe parity checking as a method of detecting errors in data transmission.

9 What is a cyclic redundancy check?

10 List five common parameters used to connect two devices.

LEARNING ACTIVITIES

1 All communication systems have five basic components. Identify the fivecomponents in these systems:a William writes a letter to a friend. He puts the letter into an envelope and sends

it through the mail system.b Julia needs to transfer the directions of a conference venue to her partner. She

draws a diagram on a piece of paper and sends it using a fax machine.

2 The 7-bit ASCII character 1011011 is to be sent with a parity bit. What is the valueof the parity bit if the parity is even? The character was received with the ASCIIcharacter of 1010001. Do you think the parity method of error detection wouldhave found the error in transmission? Why?

3 Cyclic redundancy checking is an error checking method used when transferringfiles. Explain how CRC works. Describe another method of error checking. What isone advantage of CRC over this other method?

4 A network is capable of transmitting data at 28 800 bps. How long would it taketo transmit a 400-Mb file? Characters are transmitted in 8-bit ASCII, including aparity bit and an additional start and stop bit. What is the maximum transmissionrate over the network expressed in characters per second?

5 A high school and a primary school are trying to establish a communication link.However, the link is not working. Describe any communication settings that needto be investigated to ensure correct operation. Confidential student informationis to be sent using this link. Describe any methods of securing the data duringtransmission.

6 Establish a communication link and transfer data between two computers.Describe the steps taken to establish the link.

Exercise 3.1


TeleconferencingTeleconferencing is the use of an electronic transmission to allow a meeting to occurat the same time in different locations. It is an alternative to a face-to-face meeting.Teleconferencing refers to communication, such as an audio conference or a videoconference, that goes beyond the normal telephone call between two people.• An audio conference is a single telephone call involving three or more people

at different locations. It is a service provided by a telephone company. Audiodata is transmitted and received using the existing telephone lines.

• A video conference is a meeting that allows people in different locations to seevideo images of each other on a screen, as well as hear speech. The leastexpensive form of video conferencing is a tiny camera and a 4-inch windowdisplayed on a computer screen. In a typical business video conference, peopleappear on a larger screen (see Figure 3.4). This may require specialcommunication arrangements because of the high bandwidth required totransmit video.Teleconferencing simulates a

face-to-face meeting and reducescosts. Money is saved by notbuying airfares, hotel rooms andmeals.Teleconferencing also savespeople the time and energyinvolved in travelling to attend aface-to-face meeting. Teleconfer-encing is frequently used inbusiness and distance education.However, tele-conferencing doesremove the inter-personal re-lationship achieved through aface-to-face meeting. Physicalcontact and informal discussionsare often needed to clarify ideasand develop partnerships.

Messaging systemsA messaging system is used to send messages to people in different locations whomay receive the message at a later time. It has been used for centuries in the formof letters. Messaging systems involve the creation, storage, exchange andmanagement of messages. Messages are sent to an individual or a group of people.

Traditional systemsTraditional messaging systems include the telephone and fax. They are com-munication systems used regularly by individuals and organisations.• A telephone is a system for transmitting sounds or speech between distant

locations along telephone lines. It is a convenient method of communicatingwith people around the world. A telephone answering system is a messagingsystem. It stores messages and allows a person to hear the message at a latertime.

• A fax, or facsimile, machine is a system of transmitting and reproducingdocuments by means of signals sent over telephone lines. The fax machine

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Figure 3.4 Video conferencing.

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scans a document and converts it into a bit-mapped image. This image iscompressed and transmitted along the telephone network to a destination faxmachine. This machine decompresses the image and reconstructs the originaldocument. Fax machines have become very popular as people can quicklytransfer a hard copy of a document or send a written message. Personalcomputers equipped with a fax modem are capable of performing almost allthe tasks of a fax machine.

Voice mailVoice mail, or v-mail, allows communication with other people by storing andforwarding spoken messages. The sender dials a voice-mail number and records amessage. The message is digitally stored on a computer system and can only beretrieved by the intended receiver of the message. To retrieve a message, you dialinto the voice-mail system using any telephone and enter an account number andpassword. After you enter the voice-mail system, you can listen to the message,delete it, save it or send it to another person.

Voice mail combines the features of a telephone answering system and some ofthe concepts of email. It provides some advantages over email. More people haveaccess to a telephone than to a computer equipped for email. People also oftenexpress their feelings more clearly with the spoken word. However, email is muchbetter at communicating complex information and sending different data types.

Electronic mailElectronic mail, or email, allows communication with other email users by sendingand receiving electronic messages using a computer. Email was one of the earliestuses of the Internet and is now widely used. It is fast, economical and a convenientway to send messages to people all over the world. An email message can travelaround the world in minutes. To use email, you need a computer that is linked toa network or the Internet, an account with an Internet service provider (ISP), anemail address and email software.

IITT FFaaccttIT FactThe Internet revolutionised email by turning countless incompatible net-works into one global system. It is regarded as the messaging system for the planet. Trillions of email messages are sent each year over the Internet.

Email can be written to anyone who has an email address. Email addresses areunique and are obtained free. An email address consists of two parts separated bythe @ (‘at’) symbol in the form ‘name’@‘domain name’. The first part is the nameof the account. It is often a person’s username and is chosen when a user signs upwith an ISP. If a name is already in use by someone else at the domain, the usermay have to modify his or her preferred name by adding some more letters ornumbers. The second part is the domain name. It is the location of the person’saccount on the Internet. The domain name identifies the specific computer orserver where the person’s email messages are stored. For example, in the [email protected]:• ‘nick’ is the name.• ‘ozemail.com.au’ is the domain name. ‘Ozemail’ is the ISP, ‘com’ means the

domain is commercial, and ‘au’ is Australia.


Most email messages contain two main parts: the header and the body of themessage.The header is similar to an envelope used in traditional letters. It containsinformation needed to deliver the message. The sender’s email address is usuallyautomatically inserted, just like an envelope with a pre-printed return address.Theheader contains four main parts that the sender fills in as required (see Figure 3.5):• Email address (To:) is the address of the person receiving the message. It must

be correctly typed.• Carbon copy (Cc:) sends the same message to other people apart from the

main recipient (optional).• Blind carbon copy (Bcc:) sends a copy to other people without revealing that

these other people got the message (optional).• Subject is the topic of the message or a brief description.This is very useful for

the receiver of the message (optional).

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Figure 3.5 An email message.

The body of the message is typed using the email software or is imported orcopied from a word processor. Email messages are often short and typed veryquickly. Some people use inventive spelling in emails, such as coughy, bizzy, thanxand enuff. The user does not have to be online to compose an email message.Messages can be written offline and sent when the user logs onto a LAN or theInternet. This saves money if the ISP charges by the hour for connection time.When email is sent, it is stored on the server where the recipient has an account.It stays on the server until the person checks his or her email.

After the email is read, it can be deleted, printed or stored in an appropriatefolder for later reference. The user can reply to an email message simply byclicking on the ‘reply’ icon (see Figure 3.6).The address of the receiver (the senderof the message being replied to) and the subject are automatically inserted in theheader of the reply. Leaving the subject the same identifies the ‘thread’ of themessage. The previous message can be retained so that the original senderremembers the message. This is called quoting. Forwarding messages involvessending messages you received to someone else.

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Email software provides a number of features to help users create their email.An address book is used to store email addresses (see Figure 3.7). This saves timetyping the address and avoids the problem of remembering each address. Amailing list is a group of people who may want to receive the same messages. Itmay be people working on the same project or a group of people with the sameinterests. Mailing lists are created by entering the email address of each person inthe list and giving the list a name. A signature is several lines automaticallyappended to outgoing email messages. It may include an email address, Web site,graphic, occupation or telephone number.

Figure 3.6 A reply to an email message.

Figure 3.7 An email address book.

Subject thread

EmoticonPortion of

original message‘quoted’


Electronic commerceElectronic commerce, or e-commerce, is the buying and selling of goods andservices via the Internet. It has become a multibillion-dollar source of revenue forthe world’s businesses. E-commerce provides 24-hour availability, global reach,the ability to interact and provide customer information, and a multimediaenvironment. The most popular e-commerce sites sell computer products,books, gardening products, music or office supplies (see Figure 3.8). However,e-commerce is expected to expand into most retail areas. Each day, there are newbusinesses being established that are based entirely on Web sales.

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Figure 3.8 Amazon.com is a popular e-commerce site.

EFTPOSEFTPOS (electronic funds transfer at point-of-sale) is a system that allows peopleto purchase goods and services using a credit or debit card. It is the electronictransfer of money from the customer’s bank account to the retailer’s bankaccount. EFTPOS has made shopping easier for customers and allowed retailers toimmediately receive payment for their goods. Each point-of-sale terminal is linkedto the computer of the customer’s bank using the account number on the card.Entering the PIN number is a security measure to identify the customer. When aconnection is made and approved, the money is immediately transferred.

Electronic bankingElectronic banking allows customers to view their account balances andtransaction histories, transfer money between accounts and pay bills using Bpay(see Figure 3.9). It provides banking services 24 hours a day but cannot cater forcash or cheque withdrawals. However, automatic electronic debits are becomingmore popular with consumers. Cheques are an expensive and inefficient way ofsettling debts because the cheque passes through many hands before thetransaction is completed.

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Some electronic banking providers require customers to download specialbanking software and install it on their personal computer. Electronic bankingraises the issue of security. All banks are determined to make their online bankingservices safe from inference and to secure customer details. Data encryption isused to secure the data transfer between the customer’s computer and the bank’scomputer.

Figure 3.9 Internet banking services.

1 What is teleconferencing?

2 Outline the advantages and disadvantages in teleconferencing.

3 What is a messaging system?

4 How does voice mail work?

5 Describe the two parts of an email address.

6 List the four main parts in the header of an email message.

7 Why are email messages sometimes written offline?

8 What is a mailing list?

9 Describe some the benefits of e-commerce.

10 What is provided by electronic banking?

LEARNING ACTIVITIES

1 Communication systems perform information processes requiring participants,data/information and information technology. Clearly identify the participants,data/information, information technology and the purpose of the followingcommunication systems:

Exercise 3.2


3.3 Transmitting and receivingTransmitting and receiving refers to the transfer of data and information. It iscarried out using numerous communication concepts and completed by networkhardware and software.

Communication conceptsCommunication concepts include the transmission of data, protocols, hand-shaking, networks, network topologies and network access methods.

Transmission of dataData is transferred between devices in two ways: serial transmission and paralleltransmission. Parallel transmission is the transmission of data simultaneously usingseparate channels. Serial transmission is the transmission of data one after theother. Serial transmission is used to transmit data to peripheral devices, such asmodems and printers, and is used on networks.

Serial transmission can be either synchronous or asynchronous. Asynchronoustransmission is the sending of data by identifying each byte with special start andstop bits. It has become the standard for personal computers. Part of protocolagreement is to specify how many start and stop bits.The normal range is between0 and 2. Synchronous transmission requires all the data to be sent at the same rate. The same number of bytes is sent each second. This is synchronised by eachdevice using a clock. Synchronous transmission is faster and more efficient thanasynchronous transmission as there are no extra bits. It is used on larger computersystems. (See Figure 3.10.)

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a teleconferencingb messaging systemsc electronic commerce.

2 Construct a chart to compare the advantages and disadvantages of threemessaging systems: a traditional system, voice mail and electronic mail.

3 Create a brief email message about this Information Processes and Technologycourse.a Send the email message to a partner and a carbon copy to the teacher.b Check that your partner received the email message.c Send a reply to your partner by quoting.d Forward your original message to another person in your class.

4 Create an email questionnaire on communication systems.a Design a simple questionnaire with only one or two questions.b Create a mailing list and send the email questionnaire to the mailing list.c Store the replies in a separate folder. Collate the results. A spreadsheet is a

useful tool to collate and graph the results.d Distribute the results of the survey to the people on the mailing list and thank

them for their participation.

5 David frequently uses the Internet to access information. Briefly outline the issueof copyright in relation to the Internet.

6 Kerry recently downloaded banking software for electronic banking. Describe the process of downloading. Describe two factors that affect the speed oftransmission.

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Character 7 Character 6 Character 5 Character 4 Character 3

Source

Source

Synchronous transmission

Character 6 Character 5

Startbit

0 1 0 1 0 0 1 1 1 1 0 1 1 0 0 0 1 1 1 0 0 0 0 0 01 1 1 1 1 11

1 0 0 1 0 1 1 1 1 0 1 1 0 1 0 0 0 1 0 01 1 0 0 11

Asynchronous transmission

Stopbit

Startbit

Stopbit

Startbit

Stopbit

Receiver

Receiver

Figure 3.10 Serial transmission.

The direction of data flow can be simplex, half-duplex or full-duplex mode.Simplex mode allows transmission in one direction only, from the sender to thereceiver. An example of simplex mode is the radio, a telegram or television. Half-duplex mode allows transmission in both directions but not at the same time.Thismeans the sender and the receiver take turns. An example of half-duplex mode isan intercom, walkie-talkie or disk drive. Full-duplex mode allows transmission inboth directions at the same time. Most communications systems, such as thetelephone or email, use full-duplex mode.

Protocols and handshakingA protocol is a set of rules that governs the transfer of data between computers.Protocols define how a link is established, how data is transmitted and how errorsare detected and corrected. When the same protocols are used, different types ofcomputers and other devices can communicate with each other. Numerousprotocols have been developed for specific technologies (see Table 3.1). Protocolschange over time and often are the basis for the development of a particularproduct.

When an agreement is reached about which protocol to use, it results in anexchange of information. Handshaking involves sending signals to indicate thetype of protocol to be used for an agreement to be reached. Handshaking isneeded as modems at each end of the line may have different capabilities. Forexample, they need to inform each other about and agree on the highesttransmission speed.


NetworksA network is a number of computers and their peripheral devices connectedtogether in some way. Each device in a network is called a node. The nodes in anetwork include many different types of devices, such as printers, storage devices,terminals and workstations. Terminals are devices that send data to and receivedata from another computer system. If the terminal has both memory and

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Protocol DescriptionIPX Internet Packet Exchange. A NetWare data delivery protocol used by

Novell’s NetWare Operating System.

SNA Systems Network Architecture. A protocol that defines datacommunication on a network. It was originally used to link mainframes.

FDDI Fibre Distributed Data Interface. A protocol that specifies computerinput/output interface standards using fibre-optic cables.

X.25 The standard packet switching protocol. It is used for low-speedapplications, such as credit card verifications and automatic tellermachine transactions.

ATM Asynchronous Transfer Mode. A standard transport protocol thatspecifies a method of packaging data into cells. It transmits all datatypes over any type of media.

Kermit Asynchronous communication protocol for transmission of files usingthe public telephone network.

XModem File transfer protocol developed in the late 1970s for personalcomputers. Data is transferred in blocks 128 bytes long. XModemoriginally supported checksum but later versions support CRC.

YModem File transfer protocol developed as an extension to Xmodem. Data istransferred in blocks 1024 bytes long. YModem includes such features as transfer of filenames, increased reliability of error checking andincreased data transfer.

ZModem File transfer protocol developed to rectify the limitations associatedwith YModem. ZModem uses a variable block size and supports CRC. Itprovides for high-speed packet and network communicationenvironments.

TCP/IP Transmission Control Protocol/Internet Protocol. A common set of rulesfor data transmission and error detection across the Internet. It works by breaking information into smaller packets of data.

HTTP Hypertext Transfer Protocol. A protocol that enables the user to sendand retrieve files using the Internet. HTTP allows access to Web pagesthat are based on hypertext.

FTP File Transfer Protocol. A protocol used to enable the client computer(user) to log on to the server. FTP is the oldest form of remote file access for the Internet.

POP Post Office Protocol. A protocol that specifies how email messages maybe exchanged between a computer and the ISP.

MIME Multipurpose Internet Mail. A protocol designed to enable files to besent across the Internet as email.

Table 3.1 Common data transfer protocols.

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processing capabilities, it is called an intelligent terminal. Most personalcomputers are classified as intelligent terminals and are called workstations on anetwork.

The simplest form of a network is when one computer is connected directly toanother computer, using a cable. However, a network can also consist of thousandsof computers connected together. Networks are classified as local area networks orwide area networks:• Local area networks (LANs) connect computers within a building or group of

buildings on one site. LANs cover a small geographical area, and the computersare linked together by coaxial cable or fibre-optic cable. There are three mainadvantages in using a LAN:– sharing limited hardware resources, such as printers, hard disks and modems– sharing application software, such as word processing, database, spreadsheet

and graphics programs– improved communication among users by sending electronic messages.

• Wide area networks (WANs) connect computers over hundreds or thousandsof kilometres. WANs often consist of a mainframe computer called the hostand a number of terminals. For example, the EFTPOS terminals of many retailorganisations and the ATM terminals of banks are all part of a WAN (see Figure3.11). A WAN may use a private leased line, the normal telephone network ora combination of both. A private leased line is dedicated to the network. Itoffers higher transmission speeds and more accurate transfer of data than thoseavailable through the public switched telephone network (PSTN). PSTN linksare relatively cheap if computers do not require constant connection. However,PSTN links are not guaranteed and can be interrupted.

Most data sent over a networkuses packet switching. Packetswitching is a technique thatdivides messages into small datapackets, transmits the packets andlater joins the packets to form theoriginal message. It allows multipleusers to use the same transmissionline by interspersing the datapackets from different users. Datapackets may not be sent along thesame path and could arrive at the destination at different timesand in the wrong order. Each datapacket contains an address andcontrol instruction to reassemblethe message in the correct order.Data transfer on the Internet isbased on packet switching.

Figure 3.11 EFTPOS uses a WAN.


Network topologiesNetwork topology is the physical arrangement of the devices in a network. Thereare many possible network topologies, such as star, bus and ring (see Figure 3.12).

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IITT FFaaccttIT FactThe word ‘packet’ was coined by people working on ARPANET to dividelong messages generated by their computers. The ARPANET was a networkdeveloped in 1969 by the U.S. Department of Defense that later expanded tobecome the Internet.

Figure 3.12 Common network topologies.

A star topology has a central computer with each device connected directly toit.The central computer serves as a switch. It receives messages and sends them tothe destination device. Star topology requires extra cabling because each deviceneeds a cable to the central computer rather than to the nearest device. If onedevice or cable is broken, the network can still operate. However, if the centralcomputer fails, then the network fails. It is also limited by the processing power ofthe central computer. Star networks use a time-sharing system that allocates acertain amount of CPU time for each user. It is the most common topology for a mainframe.

Bus Network

Ring Network

Star Network

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A bus topology is an arrangement where all the devices are attached to a directline called the bus. Each device has a unique identity and can only recognise thosesignals intended for it. Devices check the bus and retrieve their messages as datatravels along the bus. Each device is considered to be connected to every otherdevice and can communicate directly along the network to any other device. Bustopology is one of the easiest to set up and can still operate if one node fails.Ethernet and PowerTalk use a bus topology.

A ring topology is an arrangement where all devices are attached so that thepath is in the shape of a continuous circle. Each device in the ring has a uniqueaddress. Data flow is in one direction, moving from device to device until the dataarrives at its destination. The token ring network is the most common form ofaccess for ring topology.

Network access methodsThere are a number of ways of dealing with multiple users wanting to access thenetwork at the same time. The two most common access methods are Ethernetand token ring:• Ethernet—the first industry-standard LAN access method, or protocol, based

on a bus topology. Ethernet allows data to be transmitted simultaneously to allnodes on the network in both directions. Addressing information allows eachnode to recognise and receive individual data packets intended for it.With datapackets travelling simultaneously, collisions will occur and will cause errors. Toovercome this problem, Ethernet uses a method called Carrier Sense MultipleAccess and Collision Detection (CSMA/CD). In CSMA/CD, all nodes havethe ability to sense signals on the network. When a node wishes to transmit, it‘listens’ to the bus for signals. When there is no signals on the bus, it transmits.However, occasionally a collision will occur if two nodes sense a clear bus atthe same. When a collision is detected, each device stops transmitting and then retransmits at another time. Ethernet is defined in a standard called IEEE 802.3.

• Token ring—a LAN access method, or protocol, based on a ring topology.The token ring operates by continually passing special data packets calledtokens between nodes on the network.Workstations with data to send capturea free token and attach data along with addressing information. A busy tokenwith data cannot be used by other nodes. When the data arrives at thedestination, the data is replaced with an acknowledgment and sent back tooriginal sending node.

IITT FFaaccttIT FactA ‘phreak’ is a person who breaks into the telephone network illegally.Pheaks typically try to make free long-distance phone calls or to tap phonelines. However, the term is sometimes used to include anyone who breaks ortries to break the security of any network.

Network hardwareNetworks are not just made up of cables connected to such devices as computers,terminals and printers. Several special-purpose hardware devices are needed tosuccessfully construct a network.


Network interface cardEach computer connected to the network requires a special network interfacecard.A network interface card (NIC, pronounced ‘nick’) is an expansion card thatfits into an expansion slot of a computer or other device, so that the device can beconnected to a network. Most NICs require a network cable connection and haveconnectors on the card for different types of cables. The type of NIC dependsupon the type of network. NICs package data according to the rules of thenetwork operating system and transmit data along the connecting network cable.

ServersA server is a computer that provides services to other computers on the network.Individual computers log on to the server, which gives them access to files,applications or peripheral devices. There are different types of servers, such as fileservers, print servers, mail servers and Web servers.• A file server is a controlling computer in a network that stores the programs

and data shared by users. The files stored on this server can be retrieved by anynode provided it has access rights.

• A print server is a computer in a network that controls one or more printersand stores data to be printed. A print server can be used with or without a fileserver.

• A mail server is a computer in a network that provides email facilities. It storesincoming mail for distribution to users and forwards outgoing mail toappropriate devices.

• A Web server is a computer in a network that provides a connection to theInternet. All the Internet traffic is directed through this server.

Routers and switchesData often travels between networks.This requires networks to be linked to othernetworks, paths to be established between the networks and signal strength to beboosted.

Devices used to determine the path between networks include:• Router—a device that determines where to send a data packet between at least

two networks. Its decision is based on its current understanding of thenetworks. A router maintains a table of the available routes and theirconditions. It uses this table together with distance and cost algorithms todetermine the best route for a given data packet. Data packets often travelthrough a number of networks and routers before arriving at their destination.

• Switch—a device that directs data packets along a path. It may include thefunction of a router. In general, a switch is a simpler and faster mechanism thana router as it does not maintain knowledge of the networks. A switch is notalways required in a network. Many LANs are organised so that the nodesinspect each data packet.

Bridges and gatewaysThe actual interconnection between networks is achieved using devices such asbridges and gateways.• Bridge—a combination of hardware and software to link two similar networks.

It often connects LANs that use the same protocol, such as Ethernet. A bridge

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examines each data packet on a LAN and forwards any data packets addressedto a connected LAN. Bridges are faster than routers because they connectnetworks that are using the same protocol.

• Gateway—a combination of hardware and software to link two different typesof networks. This usually involves converting different protocols. For example,a gateway could be used to convert a TCP/IP packet to a NetWare IPX packet.

A signal may be corrupted due to long distances or interference fromelectromagnetic fields. A repeater is used to rebuild a fading signal to its originalstrength and shape before transmitting it onwards. It ensures that the data isreceived as it was sent. A network repeater is used in a LAN to connect networksegments. Repeaters are less intelligent than a bridge or gateway.

HubsA hub is a central connecting device in a network. Data arrives at the hub fromone or more devices and is forwarded out using just one cable (see Figure 3.13).For example, four cables from three computers and a printer are connected to ahub and then a single cable connects the hub to a server. A hub can also include arouter. Most hubs were originally passive.The data simply passed through the hubwithout any change. Intelligent hubs are more frequently used in today’snetworks. They often contain a CPU and network operating system. This allowsthem to perform some of the functions of a server.

Server

Switch

Switch

24 computers

Each computeron a 10 Mb/sec lin

Computers sharing10 Mb/sec line

Hub Hub Hub

High sp

eed lin

k

Figure 3.13 Network hardware.

Transmission mediaData is transferred along a transmission medium.The capacity of the transmissionmedium is called the bandwidth, and it is measured in bits per second. Atransmission medium with a high bandwidth can transfer more data.Transmissionmedia are categorised as either wire transmission or wireless transmission.

Wire transmission transfers the data through wires and cables. These cablesmust be protected from damage, they take up space, and they can be difficult toinstall. However, wire transmission can carry large amounts of data with littleinterference from other signals. Wire transmission media include twisted-pair,coaxial or fibre-optic cable (see Figure 3.14).


• Twisted-pair cable consists of two thin insulated copper wires, twisted to forma spiral. Twisting reduces the amount of interference from other cabling. Thetwo main types of twisted-pair cables are unshielded twisted-pair (UTP) andshielded twisted-pair (STP). UTP is the most common. STP is used in ‘noisy’environments where its shield protects against excessive electromagneticinterference. Twisted pair is the slowest medium, with a bandwidth up to 60 Kbps.

• Coaxial cable (or coax, pronounced ‘co-axe’) consists of a single copper wiresurrounded by an insulator, grounded shielding and an outer insulator. Theshielding allows data to be transmitted with little distortion. It is commonlyused over distances of less than a few kilometres. The bandwidth for a coaxialcable is 10 Mbps.

• Fibre-optic cable uses a laser of light to carry data in small glass fibres aboutthe diameter of a human hair. It is free from electromagnetic and radiointerference, is very secure and can transmit data at high speeds without errors.Fibre-optic cables are replacing conventional copper-wire cables. The band-width for fibre-optic cables is in excess of 400 Mbps. A single strand of opticalfibre can carry thousands of telephone conversations.

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Twisted pair

Conductor

Insulator

Coaxial cable

Outer insulation

Groundedshielding

Insulation

Inner conductor

Fibre-optic cable

Covering

Cladding

Glassoptical fibre

Figure 3.14 Wire transmission.

Most LANs use either twisted-pair cable or coaxial cable. Fibre-optic cable isusually too expensive and difficult to install.

There are two types of transmission used: baseband and broadband. Basebandnetworks use the entire capacity of the cable to transmit only one signal at a time.Most LANs are baseband. Broadband networks divide the cable so that severalsignals can be transmitted at the same time.

Wireless transmission moves the data through air and space. It does not needa fixed physical connection between the source and the destination. Radio andtelevision are examples of wireless transmission. Wireless transmission involvesmicrowaves, satellites, wireless networks and mobile phones.• A microwave is a high-frequency radio signal sent through space in a straight

line from one antenna to another. Microwaves have been used for severaldecades to transmit both voice and data. Antennas are placed on tall buildingsor mountain tops to continue transmission over long distances (see Figure3.15). Microwave transmission is faster than telephone lines or coaxial cables.Even though it is reasonably error free, weather conditions or such objects astrees and buildings can obstruct the signal and affect the transmission.

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• A satellite is a specialised receiver and transmitter that is launched by a rocketand placed in orbit around the earth. A signal is sent from one ground stationto the satellite, which receives and retransmits the signal to another groundstation. Each ground station uses a satellite dish to send and receive the signals(see Figure 3.16). Satellites can transmit large amounts of data over longdistances and at great speeds. There are hundreds of satellites currently inoperation. They are used for weather forecasting, television broadcasts, radiocommunications and Internet communications.

• Wireless LANs use radio waves, notcables, as their transmission medium.Problems in maintaining signal quality andconcerns about electromagnetic radiationhave not made wireless networks popular.• Mobile phones transmit data to a grid ofcellular stations that are linked to the wire-transmission telephone network. Mobilephones use radio waves to communicatewith the cellular station. They are portabledevices, and monthly service fees and per-call costs are higher than those for a normaltelephone in most countries.

Network softwareEach computer in a network must have appropriate network software. Thissoftware contains the ‘rules’ for communication and determines how the networkdevices send and receive data. Network software is organised by a networkadministrator.A network administrator is a person who manages a network withinan organisation. His or her responsibilities include network security, installing newapplications, distributing software upgrades, monitoring daily activity, enforcinglicensing agreements, developing a storage system and providing routine backups.These responsibilities are completed using the network operating system.

Network operating systemsA network operating system (NOS) is an operating system that is designedprimarily to support computers connected on a LAN. Some common examples ofnetwork operating systems are Novell’s Netware, Artisoft’s LANtastic andMicrosoft’s Windows NT (see Figure 3.17). One part of the network operating

Antenna

Signal

Antenna50 km

Figure 3.15 Microwave transmission.

Figure 3.16 A satellite dish.


system resides in each node and another resides in the server. The networkoperating system performs a range of different tasks.

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Figure 3.17 Windows NT Web site.

Network operating system tasksThe network operating system controls the flow of data between the devices onthe network and controls the requests for data. It organises messages from nodesuntil the network is ready to process each message. The tasks performed by anetwork operating system include:• administration—adds, removes and organises users; installs hardware devices

and software applications; and carries out maintenance operations, such asbackup

• file management—gives users access to the remote hard disks on the server andprovides a file system and the ability to manage a network directory

• applications—handles requests from users to share data and applications• resource management—allows network devices, such as printers and modems,

to be shared; assigns users to printers; and orders print jobs• security—monitors and restricts access to network resources.

Logon and logoff proceduresWhen a user connects to a network, the user is granted a certain level of access.This is done during the process of logging on. Logon is the procedure used to getaccess to the network.The user is identified by means of a user ID and a password.The user ID usually conforms to a limited length, such as eight characters; and thepassword often must contain at least one digit. The password is an importantsecurity measure and must be not be readily available or an easily guessed word,such as a nickname. The network must also keep passwords secure. The passwordfile should be encrypted and protected from unauthorised access. Network systemsmay require users to frequently change their passwords as a security measure.

98 Core

The logon procedure usually allows the user two or three attempts to enter thecorrect name and password. Mistakes can occur in typing or in the communicationlink. After logging on, the user is given access to only those features authorised bythe network administrator.

The correct procedure for logging off should always be carried out. It clears thecommunication line for another user.

IntranetsAn intranet is a private network that uses a similar interface to the Web. It usuallyhas a connection to the Internet and consists of many interlinked LANs.The mainpurpose of an intranet is to share information and computing resources among theemployees of an organisation. The information may be staff news, productinformation, telephone directories, policies, employee manuals or calendars.Whenthe intranet provides access to the Internet, it is through firewalls. Firewallsmonitor the flow of data in both directions to maintain the security of theorganisation.

An extranet is an intranet that is accessible to customers, suppliers or othersoutside the organisation. It provides such information as product descriptions,answers to frequently asked questions, warranties and how to contact customerservice. Organisations are attempting to make extranets easy to use and a sourceof relevant information.

IITT FFaaccttIT FactInfosurfing is using the Internet to get the maximum information in theshortest amount of time. It favours textual content over images. Infosurfingis practiced by people who become impatient waiting for multimedia to loador who just need to focus on text.

1 Explain the difference between simplex, half-duplex and full-duplex mode.

2 Describe the function of a protocol.

3 Explain the difference between the YModem and the ZModem protocols.

4 Describe an X.25 protocol.

5 What is the difference between a LAN and a WAN?

6 Describe the advantages of using a private leased line.

7 What is packet switching?

8 Explain the difference between a bus topology and a ring topology.

9 Describe the way a LAN transmits messages using an Ethernet and using a tokenring.

10 Describe the collision-detection mechanism used on an Ethernet.

11 Describe four different types of servers.

12 How does a router determine where to send a data packet?

13 Explain the difference between a bridge and a gateway.

14 What is a hub?

Exercise 3.3

Communication systems 99

15 Describe three methods of wire transmission.

16 Explain the difference between baseband and broadband.

17 Describe microwave as a transmission medium.

18 What are the responsibilities of the network administrator?

19 Describe the tasks performed by a network operating system.

20 Describe the process of logging on to a network.

21 What is the main purpose of an intranet?

LEARNING ACTIVITIES

1 Gloria connected to a remote computer. She used the following communicationsettings: 7-bit ASCII, 1 start bit, 1 stop bit, odd parity, and 4800 baud. What is thistype of transmission? Explain the type of error detection method used in thisconnection. What is one major deficiency of this method? Describe an alternativeerror detection method that would provide better results.

2 A LAN is to be constructed with seven nodes, using a ring topology. Draw adiagram to show this arrangement. How will this network transfer data? Describehow the network will overcome the problem of multiple users.

3 The management of a large organisation has decided to connect two LANs. Whatare some of the benefits to the organisation if the LANs are linked? One LAN usesthe Ethernet protocol and the other a token ring protocol. Name a device thatcould be used to connect the LANs. What does this device do?

4 An organisation is planning to introduce two LANs, one in each of two differentbuildings on the same site. These networks are to be linked together. Theorganisation decides to install a bus network for both LANs. Draw a diagram toshow this arrangement. How will each LAN transfer data? Describe how thenetwork will overcome the problem of multiple users. Describe a device that couldbe used to connect the two LANs.

5 A large organisation uses a LAN that has a bus network topology. The network hasa file server, one print server, a printer and six workstations. Draw a sketch of thisnetwork. Describe the function of the print server. A mail server is to be added tothe network. What is the function of a mail server? Describe any procedures thatcould be used to provide security for files on the network.

6 Investigate a LAN either at your school or in the local community. Draw thetopology of the LAN. Describe the advantages of this network topology over othertopologies. List the types of problems likely to be encountered on this type ofnetwork. What network software controls the functions of this LAN? List the tasksperformed by the network software.

7 Explain the differences between an intranet and the Internet for transmitting andreceiving information in a communication system. What do these communicationsystems have in common?

100 Core

3.4 Other information processesAll information processes play a role in communication systems, includingcollecting, processing and displaying.

CollectingCollecting data for a communication system involves generating the data to betransmitted. For example, a person using an ATM generates data by inserting atransaction card and typing a request on a keyboard. This data is collected andtransmitted to the bank’s computer. Another example is when a salesperson in ashop scans the barcodes of a product. The product’s details are collected andtransmitted to a central computer.

Collecting data involves a range of collection devices to gather different typesof data. The choice of device depends on the application and the type of data tobe transmitted. Some collection devices include:• ATM terminals for electronic banking• EFTPOS terminals for a retail store• telephones for voice mail• keyboards for electronic mail• video cameras for a surveillance system.

IITT FFaaccttIT FactInternesia is an inability to remember on which Web site an item ofinformation was located. People suffering from internesia often bookmarkso many sites that they cannot find anything by using their bookmark list.

ProcessingIn a communication system, processing data is the manipulation of the data.Afterthe data is collected, it must be converted into a form for transmission. Thisprocess involves encoding and decoding.

Encoding and decodingEncoding involves converting data from its original form into another form fortransmission. Decoding is the reverse process. It converts data from the form usedfor transmission back into the original form. For example, a telephone encodes thesounds from your voice into electrical pulses that can be transmitted along thetelephone lines.The telephone receiving the call decodes the electrical pulses backto the sounds of your voice. The type of encoding and decoding depends onwhether the original data is in analog or digital form.

Analog data is represented by using continuous variable physical quantities,such as voltages. For example, a clock that displays the time by hands movingsmoothly around the clock face is an analog device.At any moment, the clock willgive you an instant measure of the exact time, since you can estimate parts of asecond as the second hand moves. Most natural events in the real world, such astemperature, light and pressure, are in analog form. They change smoothly andslowly like the hands of the clock. Sounds, images and video are naturally in analogform. Analog signals are pulses, usually electrical or optical, in the form of acontinuous wave.


Digital data is represented in the form of digits or numbers. For example, adigital clock shows the time as a certain number of hours and minutes. The timechanges in a series of jumps. Numbers, text and other characters are naturally indigital form. Information technology works with data in a digital form. Digitalsignals are represented as a series of 0s and 1s.

The form of the data (either analog or digital) and the transmission signal(either analog or digital signal) affects the quality of the data received and the costof transmission.The quality of analog data depends on maintaining the exact waveas it moves through a wire or space. If it is corrupted in any way, there is no wayof regenerating the wave. However, digital data is transmitted as a series of 0s and1s, and it is possible to regenerate data that has been corrupted. That is, toreconstruct the data, it is only necessary to distinguish between a 0 and a 1.As discussed previously, common methods for error detection include paritychecking, checksum and cyclic redundancy check.

There are four encoding and decoding possibilities in transmission:• Analog data to analog signal. The wave shape of the data is encoded into the

signal. A telephone encodes analog data in the form of sounds into analogsignals suitable for the telephone line. If the signal is corrupted, there is no wayof restoring the original analog data.

• Digital data to analog signal.A series of 0s and 1s is encoded into a continuouswave. A modem encodes (or modulates) digital data from a computer intoanalog signals for the telephone line. When the analog signal is received byanother modem, it decodes (or demodulates) the analog signal into digital data(see Figure 3.18).

• Digital data to digital signal. A series of 0s and 1s is transmitted by sending itthrough a channel as a series of on and off pulses. Data transmitted in a LANis digital data using a digital signal. There is a low error rate for this type oftransmission. Digital data is encoded (changed) into a digital signal by thecomputer or a specific peripheral device.

101

Computer

Modem

Modem

Phone line

Digital signal

Analog signal

0 0 0 0 0

1 1 1 1 1

Digital signal

0 0 0 0 0

1 1 1 1 1

1 0 1 0

Computer

Figure 3.18 A modem encodes digital data to analog signals and decodes analog signals to digital data.

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• Analog data to digital signal—the wave shape of the data is encoded into aseries of 0s and 1s. This process of generating digits or numbers is calleddigitising. Images are digitised using such devices as scanners, and sounds aredigitised using a process called sampling. The transmission of television using acable is an example of analog data to digital signal.

AttachmentsAttachments are computer files, such as text, video, sound, pictures or programs,sent with an email message. Clearly, the receiver of the email must have anapplication that can read or convert the file. When sending attachments, it isimportant to include a brief explanation in the main body of the email. Theexplanation should state that there is an attachment and give its filename and its format.

All email programs need to ‘encode’ file attachments into characters since theInternet TCP/IP protocol does not allow transmission of binary code. Many emailprograms use the Multipurpose Internet Mail Extension (MIME) protocol to dothis. It is an Internet protocol that is able to negotiate many different operatingsystems and types of software. It has been a major step forward in the ability toexchange files other than plain-text files.

Client-server architectureClient-server architecture describes the software relationship between the client(user) and the server. A client sends a request to a server according to an agreed

protocol, and the server responds. It issimilar to a customer (client) sendingan order (request) on an order form(protocol) to a supplier (server) forparticular goods (data). Client-serverarchitecture provides a convenient wayto interconnect programs that are distributed across different locations ofa network. Most business applicationstoday use a client-server architecture, asdoes the Internet.The Web browser is aclient program that requests servicesfrom a Web server to complete therequest. Ideally, a server should providea user-friendly interface so that clientsare not aware of the information technology that is providing the service.

DisplayingDisplaying is the presentation of information in the form of text, numbers, images,audio or video. A range of hardware and software combinations can be used todisplay different types of information in a communication system such as atelephone and an EFTPOS terminal:


• Telephone. Audio information is displayed using a telephone. A telephonecontains a transmitter that converts sound into a signal suitable for thetransmission medium and a receiver that converts the signal back into sound.When a message is retrieved from voice mail, the telephone is the displaydevice used to listen to the message.

• EFTPOS terminal. Information about EFTPOS transactions is displayed usingan EFTPOS terminal. The EFTPOS terminal contains a screen to display thename and price of the product being purchased.When the customer’s bank hasbeen contacted, then the EFTPOS terminal displays the approval if funds areavailable. The EFTPOS terminal provides a receipt for the customer of alltransactions.

103

IITT FFaaccttIT FactNetscape sometimes uses a cartoon character called Mozilla as a mascot forits products. Mozilla was Netscape’s original name for Navigator. It wasused by Navigator’s developers as a follow up to Mosaic.

1 List five collection devices used in communication systems.

2 Explain the difference between encoding and decoding.

3 What types of data are naturally in analog form?

4 How are digital signals represented?

5 Describe the processing of digital data to an analog signal.

6 Describe the processing of analog data to a digital signal.

7 How does the client-server architecture work?

8 Describe the Internet as a client-server architecture.

9 What information is displayed by an EFTPOS terminal?

LEARNING ACTIVITIES

1 What is the difference between an analog and a digital signal? Draw a diagram toillustrate your answer. Describe one device that converts analog and digital data.

2 Information resources sharing is usually provided by a file server or a client servermethod. Illustrate the difference between these methods when a request is madeto an account file for all customers who have a balance of over $5000.

3 EFTPOS terminals are used to carry out some of the information processes in acommunication system. Examine EFTPOS terminals and classify the procedures interms of the information processes.

4 Create an email message that contains an attachment, such as a simple graphic.The email is to contain a brief explanation of the attachment.a Send the email message to a friend and a carbon copy to the teacher.b Check that your friend received the email message and could open the

attachment.

Exercise 3.4

104 Core

IITT FFaaccttIT FactThe volume of information that is absorbed in one week at the end of the20th century is more than a person received in a lifetime at the beginning ofthe 20th century.

3.5 Issues related to communication systemsBoth positive and negative impacts arise in the use of communication systems.In this section, we examine some of the social and ethical issues raised bycommunication systems.

Messaging systemsMessaging systems have improved communication between people; however, theyhave raised a number of issues:• Social context. Ideas delivered by messaging systems appear less forceful and

caring than ideas delivered personally. Messaging systems have difficulty whencommunication depends on users expressing their feelings.

• Danger of misinterpretation. Communication often depends on the context,inflection in the speaker’s voice, and body language. For example, ‘this has beena great day’ could have a negative or a positive meaning depending on the waythe words are spoken.This phrase could easily be misinterpreted using email ora fax. There are also dangers with voice mail and the telephone, as bodylanguage is not communicated.

• Power relationships. Messaging systems may change the relationship betweenpeople in an organisation. For example, email could provide an easy avenue forthe lowest paid worker of an organisation to provide information to the seniormanager.The normal method of communication through middle managementis affected.

• Privacy and confidentiality. A characteristic of messaging systems is that themessages are stored. Email and voice mail store messages on servers, and thesecan be accessed by the people who are providing the service. Hackers may alsobreak the security of these servers.Telephone conversations can be intercepted,and fax messages can be read by anybody near the machine. Clearly, messagingsystems do not guarantee the privacy and confidentiality of messages.

• Electronic junk mail. Unwanted mail is a problem for messaging systems.People can send an email message to one person or thousands of people(spamming) very easily. It may simply be a message about a product or service.However, if a person receives hundreds of junk emails each day, it takes upvaluable time. Prohibiting this practice would be difficult and compromise our free society.

• Information overload. This term refers to the enormous amount of informationthat people have to absorb. Messaging systems are a source of information. Thelarge amount of email and voice mail received by some people has increasedtheir workload and caused stress.There is often an expectation that people willrespond more quickly to email and voice mail than to a letter or to a telephonemessage written down by someone else.


InternetMany social and ethical issues have been raised by the use of the Internet. Someof the issues include Internet trading, censorship and Internet banking.

Internet tradingInternet trading, or e-commerce, is increasing at a staggering rate to meet theneeds of consumers. Most experts predict that Internet trading and the number ofcustomers on the Net will continue to rise in the next few years. E-commerce ispresently valued at approximately $200 billion. Many businesses are establishinga Web site to promote their goods and services. The Internet provides significantadvantages for consumers, such as more information about products and services,shopping globally and increased competition that has resulted in lower prices.Some of the implications of Internet trading include:• Taxation. Present governments have been unable to tax transactions on the

Internet. The increased business on the Internet will reduce the moneygovernments receive from their goods and services taxes.

• Employment ramifications. The increase in Internet trading requires morepeople to be employed in the information technology industry. It may result infewer shop fronts and fewer people employed to provide this type of service.

• Nature of business. Traditional businesses that provide opportunities forhuman interaction are being challenged. For example, people are choosing tobuy their groceries using the Internet instead of visiting the store (see Figure3.19). People can complete some of their business at home without the hassleof travelling.

• Trade barriers. The developments in communication technology have madetrade barriers between countries irrelevant. The whole issue of where onecountry ends and another one begins is open to question. People are buyingand selling goods on the Internet with little thought given to the countriesinvolved or to trade barriers.

105

Figure 3.19 Internet shopping.

106 Core

CensorshipOne of the most controversial issues to have arisen with the Internet is censorship.The Internet provides access to a large amount of offensive material, such aspornography, racism and violence, and the information is not hard to find. TheInternet allows children to access any material they wish, either deliberately orunintentionally. Some people believe that offensive material should be banned,while others argue that banning any material compromises our free society.

There have been many unsuccessful attempts to censor material on the Internetby governments and law enforcement bodies all around the world. The InternetIndustry Association (IIA) represents Australian ISPs (see Figure 3.20). It hasreleased a code of conduct that deals with censorship of online content. The coderequires ISPs to remove offensive content from their servers and to block access toclassified material hosted on overseas sites.The federal government has passed a lawrequiring ISPs to subscribe to the IIA’s code.The difficulty with enforcing censorshipis the enormous number of Web sites and the fact that thousands of new sites arepublished daily. Monitoring Web sites on a global basis is impossible. Clearly multi-national agreement is needed on offensive material. However, this agreement maybe difficult to obtain and regulate. The prime responsibility for preventing childrenfrom accessing offensive material rests with parents and teachers.

Figure 3.20 The IIA’s Web site provides access to the IIA’s code of practice.

Internet bankingInternet banking allows customers to view their account balances and transactionhistories, transfer money between accounts, and pay bills using Bpay. It providesbanking services 24 hours a day but cannot cater for cash withdrawals or for cashor cheque deposits. Issues arising from Internet banking include:• Security. All banks are determined to make their online banking services safe

from inference and secure for customer details. Data encryption is used to securethe data transfer between the customer’s computer and the bank’s computer.

• Changing nature of work. People working for the bank are not carrying out theservices provided by Internet banking. Banks require more people withinformation technology skills and fewer people with banking skills.


• Branch closures and job loss. With many customers using Internet banking,EFTPOS and ATMs, there is less need to access the facilities provided by a bankbranch. This has resulted in branch closures and job losses.

Radio and videoThe number of services delivered by the Internet is rapidly increasing. Twoexamples of this development are radio and video. There are currently thousandsof Web sites broadcasting radio from around the world. These radio stations caterfor a variety of tastes. For example, it is possible to listen to a major sporting eventlive on the Internet. In addition to the Internet providing radio services, there aremany Web sites with video.

Video on the Internet is replacing videotapes and other media. It allowsorganisations to create unlimited video channels. These video channels are usedfor sales, training, communication and a host of other purposes. Video on theInternet saves time, reduces costs and provides the ability to view the videoglobally. The size and quality of the video is currently less than that of a normaltelevision broadcast; however, it will improve with developments in technology,such as increasing bandwidth.

107

Working from homeCommunication systems have led to an increase in the number of people whoeither choose or are asked to work from home. This is called telecommuting.Telecommuting is working at home and electronically communicating with theoffice (see Figure 3.21). Even though working at the office is not likely todisappear, advances in telecommunication are likely to make telecommuting morecommon in the future. Factors that willaffect the future of telecommutinginclude the availability of bandwidth,the perceived value in telecommuting,and the opportunities to workcollaboratively across large distances.The Internet has provided the means fora new type of organisation to developwhose employees work almost entirelythrough telecommunication with anoccasional face-to-face meeting.

The main advantages of tele-commuting are greater flexibility in workhours; saving money on transport,clothing and food; and saving time. Inparticular, it benefits people who arephysically impaired or required to lookafter small children. The employer saveson overheads, such as office space andfurniture. However, working from home

IITT FFaaccttIT FactA ‘mouse potato’ is an Internet user who spends an excessive amount of timeonline and is addicted to the Internet. It comes from the term ‘couch potato’.

Figure 3.21 Working from home.

108 Core

can have its disadvantages. People can miss the social and professional contactoffered by an external place of work. They experience feelings of loneliness andisolation. Telecommuting can also blur the distinction between work and homelife. The home is no longer a place where the pressures of work can be forgotten,and work may be interrupted by domestic chores. There are many other issuesthat arise when people work from home, such as:• Is there going to be a greater investment in the equipment needed to cater for

telecommuters? • Who is responsible for the maintenance of the equipment used in the home?• Does the telecommuter have the same loyalty to an employer as an employee

working in an office?• How secure are sensitive documents in the home?

1 Why is there a danger of misinterpretation with messaging systems?

2 How are privacy and confidentiality a concern with messaging systems?

3 What is electronic junk mail? Why is it a problem?

4 Why are businesses establishing a Web site?

5 What is the effect of Internet trading on employment?

6 How are trade barriers affected by Internet trading?

7 Describe the method used by the IIA to deal with offensive material on theInternet.

8 Describe three issues that have arisen from Internet banking.

9 Why is video used on the Internet?

10 Outline the advantages and disadvantages of telecommuting.

LEARNING ACTIVITIES

1 Outline some of the changes to the banking industry as a result of newcommunication systems. Are these changes positive or negative? Give a reason foryour answer. How have these changes affected the nature of jobs in the bankingindustry?

2 Alanna finds it convenient to shop on the Internet. However, she is concernedabout the issue of security. Explain why security is a problem. Describe twomeasures that have been taken to overcome these security problems. Investigatethe issue of security by searching the Internet. Compare your results with anotherstudent in your class.

3 ‘Information technology has resulted in people spending more time inside theirhouses and less time exploring the world.’ Discuss this statement in terms ofdevelopments in communication systems.

4 Communication systems are having positive and negative impacts on our society.Briefly describe some of the changes to our society caused by communicationsystems. What do you think is the greatest concern with communication systems?Give a reason for your answer.

5 ‘Offensive material should be banned from the Internet.’ What is your view oncensorship of the Internet? Give reasons for your answer.

Exercise 3.5

Chapter review

Communication systems 109

PART A


1 Cyclic redundancy check is an errordetection method that:A uses a division processB counts the number of bits in a data

packetC checks for redundant dataD performs a check in cycles

2 A seven-bit ASCII character 1001011was sent with a parity bit of 1. Thecharacter was received as the ASCIIcharacter 1000011 and a parity bit of 1.A Data was sent using an even parity

and interpreted as correctB Data was sent using an even parity

and interpreted as incorrectC Data was sent using an odd parity

and interpreted as correctD Data was sent using an odd parity

and interpreted as incorrect

3 The baud rate is the:A number of bits that can be trans-

mitted in one secondB transmission of data at the same rateC maximum number of data symbols or

electrical signals that can transmittedin one second

D number of bauds that can be trans-mitted in one second

4 LANs often store application softwareon more a powerful computer called a:A Web serverB mail serverC file serverD print server

5 A person uses a debit card to purchasegoods in a shop. The transaction detailsare transferred to the bank’s computer.This data is protected during trans-mission by:

A a passwordB protected transmission mediaC data encryptionD a firewall

6 A combination of hardware and soft-ware to link two similar networks:A bridgeB switchC hubD router

7 A data packet is sent through a LAN to a terminal. The data packet passesthrough each node until it reaches theterminal or returns to the sender. Thenetwork topology is a:A starB ringC busD TCP/IP

8 XModem and ZModem are:A file transfer protocolsB types of modemsC error checking methodsD network access methods

9 Each device in a network is called a:A nodeB terminalC serverD workstation

10 The bandwidth, from lowest to highest,is:A fibre-optic cable, coaxial cable, micro-

waveB coaxial cable, microwave, fibre-optic

cableC microwave, coaxial cable, fibre-optic

cableD coaxial cable, fibre-optic cable, micro-

wave



Statements

1 A method of checking for errors in datatransmission using a division process.

2 A set of rules that governs the transferof data between computers.

3 A network topology that uses a centralcomputer with each device connecteddirectly to it.

4 The number of bits that can be trans-mitted in one second.

5 Data represented in the form of digitsor numbers.

6 An agreement that results in the ex-change of information.

7 A method of checking for errors in datatransmission by counting the number ofbits in a data packet.

8 A central connecting device in a net-work.

9 It allows communication with otherpeople by storing and forwardingspoken messages.

10 LAN access method that allows data to be transmitted simultaneously to all nodes on the network in bothdirections.

11 It allows communication with otherusers by sending and receiving elec-tronic messages using a computer.

12 The maximum number of data symbolsor electrical signals that can transmittedin one second.

13 A network topology where all devicesare attached so that the path is in theshape of a continuous circle.

14 A device that directs data packets alonga path.

15 Data represented by using continuousvariable physical quantities, such asvoltages.

List of terms

a analog i handshaking

b baud rate j hub

c bps k protocol

d checksum l ring

e CRC m star

f digital n switch

g email o v-mail

h Ethernet

PART C

Write at least one paragraph on each of thefollowing questions.

1 What is a communication system? List the five basic components of acommunication system. Identify thesecomponents when using email.

2 One method of error detection is paritychecking. How does this method work?Describe one specific error that a paritycheck would fail to detect.

3 Explain the difference between thefollowing pairs of terms:a Coaxial cable and fibre-optic cableb Host computer and terminalc Asynchronous and synchronousd Error detection and error correction.

4 Briefly describe the three networktopologies.

5 Draw a diagram to explain thecommunication link between twocomputers. It should illustrate anyencoding and decoding that is carriedout by the link.

6 Identify a social and ethical issueinvolved in a communication system.Outline both the positive and negativesides of the issue.

110 Core

OptionsChapter 4 Transaction processing systemsChapter 5 Decision support systemsChapter 6 Automated manufacturing systemsChapter 7 Multimedia systems

44TRANSACTIONPROCESSINGSYSTEMS

cchhaapptteerr






• demonstrates ethical practice in the use ofinformation systems, technologies and pro-cesses (H3.2)



Outcomes

This chapter examines the characteristics oftransaction processing systems. It investigatesspecific examples of real-time transaction pro-cessing and batch transaction processing. Theinformation processes of storing and retrieving,collecting, and analysing for a transaction pro-cessing system are examined. The chapterconcludes by outlining the social and ethicalissues that relate to transaction processingsystems.

Overview

Transaction processing systems

4.1 Characteristics of transactionprocessing systemsTransaction processing systems (TPSs) collect, store, modify and retrieve thetransactions of an organisation. A transaction is an event that generates or modifiesdata that is eventually stored in an information system. Some examples of TPSsare selling goods using a point-of-sale (POS) system, processing credit cardpayments, or making a motel reservation.TPSs differ in character from other typesof information systems in that they directly support business operations. Theymust be designed in conjunction with the organisation’s procedures. The trans-action data obtained from a TPS is stored in an information system and processedusing a range of application software. It usually involves updating a database toreflect changes to the transaction data.

The main information processes of a TPS are collecting and storage. If a TPS isused to record a sale and generate a receipt, the transaction data is collected at thePOS terminal and then stored using an online database. The four importantcharacteristics of a TPS are rapid response, reliability, inflexibility and controlledprocessing.• Rapid response. Fast performance with a rapid response time is critical.

Businesses cannot afford to have customers waiting for a TPS to respond. Theturnaround time from the input of the transaction to the production of theoutput must be a few seconds or less.

• Reliability. Many organisations rely heavily on their TPS. A breakdown willdisrupt operations or even stop the business. For a TPS to be effective, itsfailure rate must be very low. If a TPS does fail, then quick and accuraterecovery must be possible. This makes well-designed backup and recoveryprocedures essential.

• Inflexibility. A TPS wants every transaction to be processed in the same wayregardless of the user, the customer or the time of day. If a TPS were flexible,there would be too many opportunities for non-standard operations. Forexample, a commercial airline needs to consistently accept airline reservationsfrom a range of travel agents. Accepting different transaction data fromdifferent travel agents would be a problem.

• Controlled processing. The processing in a TPS must support an organisation’soperations. For example, if an organisation allocates roles and responsibilitiesto particular employees, then the TPS should enforce and maintain thisrequirement.A TPS minimises the organisation’s costs by reducing the number of times that

data must be handled and by providing timely updates to the database. There aretwo types of transaction processing: batch transaction processing and real-timetransaction processing

113

114 Options

Batch transaction processingBatch transaction processing collects the transaction data as a group, or batch, andprocesses it later. It has a time delay. Transactions are collected and held forprocessing until it is convenient or economical to process them.Waiting for a largevolume of data generally results in lower processing costs per transaction. Thetransactions are collected and stored offline on a magnetic tape or on paper. Thetime delay before processing or completing a batch run could be several minutes,hours or even days. For example, the clearance of cheques is a batch process thattakes several days. Batch processing is used when a time delay will not decreasethe usefulness of the results. A batch approach is used for generating pay chequesand other forms of paper output.

IITT FFaaccttIT FactThe term ‘batch’ originated when punch cards were the usual inputmedium. A batch of cards represented a computer program and was storedin sequence in a box. A computer operator fed the cards into the computer.The output was obtained the next day.

Batch processing is carried out by large organisations using a mainframe ormid-range computer (see Figure 4.1). It involves a large batch of an identical datatype, such as payroll or stock information. For example, a payroll applicationcollects data for each employee, such as the hours worked and overtime earned.This data is processed in batches by updating a payroll master file. After themaster file is updated, the pay slips are created for all employees in the organi-sation. Batch programs are often run at night when there is less demand for the information system. There are three disadvantages in batch processing:• All processing must wait until a set time. The processing schedule is pre-

determined.• Errors cannot be corrected during processing.• Sorting the transaction data is expensive and time consuming.

Figure 4.1 Batch processing using a mainframe computer and magnetic tape.


Batch transaction processing was the only feasible form of transactionprocessing when data was stored on punch cards or tapes. However, advances ininformation technology have resulted in the ability to do real-time transactionprocessing.

Real-time transaction processingReal-time transaction processing is the immediate processing of data. It providesinstant confirmation of a transaction but does require access to an online database.Real-time processing involves using a terminal or workstation to enter data anddisplay the results of the TPS. It uses a computer network to link the terminals tothe mainframe computer and to access the online database. Real-time processinginvolves a large number of users who are simultaneously performing transactionsto change data. Even though each individual user is processing a relatively smallnumber of records, their requests are being made at the same time. Two commonexamples of real-time processing are airline reservation systems and bankingtransaction systems.

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IITT FFaaccttIT FactReal-time transaction processing is often called OLTP (online transactionprocessing). An online database is updated as the result of a businesstransaction.

The two main concerns with real-time processing are concurrency andatomicity.• Concurrency ensures that two users cannot change the same data at the same

time. That is, one user cannot change a piece of data before another user hasfinished with it. For example, if an airline ticket agent starts to reserve the lastseat on a flight, then another agent cannot tell another passenger that a seat isavailable.

• Atomicity ensures that all of the steps involved in a transaction are completedsuccessfully as a group. If any step fails, no other step should be completed. Forexample, a banking transaction may involve two steps: withdrawing moneyfrom a cheque account and transferring it into a savings account. If the firststep (the withdrawal) succeeds, then the second step (the transfer) mustsucceed; otherwise, the entire transaction is abandoned. This ensures that thewithdrawal isn’t recorded twice and the transfer only once.Every real-time TPS has a user response-time delay caused by its transaction

processing activities. For a TPS to be classified as ‘real-time’, the response-timedelay must be acceptable for that application. For example, a computer systemcontrolling an aircraft guidance system requires a response time limited to afraction of a second. However, in an airline reservation system, a response time ofseveral seconds would be satisfactory. In this case, instantaneous access to any orall of the data is either unrealistic or uneconomical. The main disadvantageassociated with real-time processing is the tremendous expense. Both the hard-ware and software costs of this type of processing exceed those of batchprocessing.

116 Options

Transaction processing monitorA transaction processing monitor (TP monitor) is software that allows thetransaction processing application programs to run efficiently. It manages thesequence of events that are part of a transaction.A TP monitor provides a standardinterface between the input devices (such as terminals), the transaction processingapplication programs, and the DBMS. It also provides data security by ensuringthat transactions do not get lost or corrupted.A TP monitor is used in conjunctionwith a particular operating system.

Real-time and batch processingThere are a number of differences between real-time and batch processing. Theseare outlined below:• Each transaction in real-time processing is unique. It is not part of a group of

transactions, even though those transactions are processed in the same manner.Transactions in real-time processing are stand-alone both in the entry to thesystem and also in the handling of output.

• Real-time processing requires the master file to be available more often forupdating and reference than batch processing. The database is not accessibleall of the time for batch processing.

• Real-time processing has fewer errors than batch processing, as transaction datais validated and entered immediately.With batch processing, the data is organisedand stored before the master file is updated. Errors can occur during these steps.

• Infrequent errors may occur in real-time processing; however, they are oftentolerated. It is not practical to shut down the system for infrequent errors.

TerminalTerminal Terminal

User Interface

TP Monitor

Application

DBMS

Database

Figure 4.2 Real-time transaction processing.


• More computer operators are required in real-time processing, as theoperations are not centralised. It is more difficult to maintain a real-timeprocessing system than a batch processing system.

Data validationData validation is used to check the entry of transaction data. It involves pro-cedures to ensure that transactions are correct and have been accurately stored inthe database. Data validation involves transaction initiation and field checking.• Transaction initiation is used to acknowledge that the TP monitor is ready to

receive the transaction data. It is used in real-time processing to eliminate anumber of possible errors. Some TPSs add an entry time to the transaction datain an attempt to trace the data if it is lost.

• Field checking occurs when the transaction data is entered into a database.Thedata is organised into files, records, fields and characters. Data validation iscarried out by checking the fields, using a range check, list check, type check orcheck digit as described in Chapter 2.Even though data validation is essential, it is impossible to validate all the data

in the system. For example, a user may incorrectly type ‘45’ instead of ‘54’. Thissimple transposition is often difficult to detect. There may be no reason toquestion this type of error.

Historical significance of transaction processing systemsTransaction processing was the first type of information system. TPSs were usedduring the 1950s when the electronic computer became available for business use. The first commercially available electronic computer was called UNIVAC(Universal Automatic Computer). It was designed by John Presper Eckert andJohn William Mauchly. The first UNIVAC was delivered to the U.S. Bureau ofCensus. It could process both numerical and alphabetical calculations with ease.UNIVAC was used by organisations to batch process business transactions, such aspaying employees and recording customer purchases and payments. These initialapplications of a TPS are still important today.

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Figure 4.3 UNIVAC.

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Manual transaction systemsManual transaction systems are business systems that operate without the use ofmachines. People are used to record the data about the business activities. Forexample, a manual POS system has eleven operational steps performed by a salesassistant to sell a product to a customer:1 Examine the product and determine the product price.2 Record the product price on the sales slip and add it to the total price of all

selected products.3 Repeat steps 1 and 2 for subsequent products.4 Check the total price of all the products selected.5 Inform the customer of the total price and wait for payment.6 Receive payment for the products.7 Calculate the amount of change owing to the customer.8 Give the selected products, a copy of the sales slip, and the change to the

customer.9 Repeat steps 1 to 8 for the next customer.

10 At the end of the business day, total all sales slips to check that the moneycollected is correct.

11 Do a stocktake to count all products remaining. Check that the stockremaining equals the stock at the beginning of the business day minus thestock sold.The manual POS system is typical of a manual transaction system. It is based

on a clear set of rules that is followed by a person. These rules, or procedures, in amanual transaction system allow the system to be easily computerised. Theprocedures that can be computerised are identified by the data they are pro-cessing. In the manual POS system, the data being processed is the price ofproducts sold and the receipt of payments. The manual procedures that collect,manipulate and store this data (steps 1, 2, 4, 6, 7, 10 and 11) could becomputerised. A transaction is made up of steps 1, 2, 4, 6 and 7. These steps mustbe completed before the transaction is considered successful. Steps 10 and 11update the organisation’s financial position and its stock inventory. They verifythat the money collected and the remaining stock are correct. They give theassurance that the business has not had any money or stock misplaced or stolen.A stocktake is a simple procedure but very labour intensive when done manually.

Computerisation of a manual transaction system provides significant benefitsto the business. First, it increases the rate at which products are sold. There is lesstime taken for a customer to purchase a product. Customers are not waiting for aperson to complete the manual procedures. A second benefit is that it providesinformation on which products are in demand.The business knows what productsare selling from the inventory database. After a period of time, the business canmodify its range of products to suit its customers’ purchasing habits. Com-puterisation of a manual transaction system aims to maximise the profits of thebusiness. The design of a TPS should be based on detailed specifications of howtransactions are performed and how to control the collection of data. Thetransaction data must be collected in a specific format and must match theoperation of the organisation.


4.2 Examples of transactionprocessing systemsIn this section, we examine the components of a TPS and examples of real-timetransaction processing and batch transaction processing.

Components of a transaction processing systemPeople are an important component of a TPS. They can be classified as users,participants, and people in the environment:• Users of a TPS often take the data provided by the TPS and use it in another

type of information system.This is a main feature of a TPS. For example, a POSsystem could provide stock inventory that is used by an automatedmanufacturing system. The users of the other information systems belong tothe same organisation that owns the TPS.They are not interacting with the TPS

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1 What is a transaction processing system?

2 How do TPSs differ in character from other types of information systems?

3 Describe four important characteristics of a TPS.

4 What is batch transaction processing?

5 List three disadvantages of batch processing.

6 What is real-time transaction processing?

7 Explain the difference between concurrency and atomicity.

8 What is the main disadvantage associated with real-time processing?

9 Describe a TP monitor.

10 Why does real-time processing have fewer errors than batch processing?

11 Why are infrequent errors in real-time processing often tolerated?

12 List some ways in which data is validated in a TPS.

13 Why is it impossible to validate all the data?

14 When were TPSs first used?

15 Describe the benefits of computerising a manual transaction system.

LEARNING ACTIVITIES

1 Identify a batch transaction processing system. Describe the steps in its operation.What information technology is used in this TPS? Distinguish between the storageof the collected data and the storage of the processed data.

2 Identify a real-time transaction processing system. Describe the steps in itsoperation. What information technology is used in this TPS?

3 Compare and contrast batch and real-time transaction processing.

4 Analyse an existing TPS and determine its strengths and weaknesses.

5 Search the Internet for information on UNIVAC. Describe its technical and physicalfeatures. Why was the UNIVAC an important development for transactionprocessing?

Exercise 4.1

120 Options

but are using the data provided by the TPS. Managers often take the data froma TPS and use it in other information systems to make strategic decisions.

• Participants are the people who conduct the information processing. They arethe people who do the work. Participants need to know what to do, how to doit and when to do it. They have an essential role in a TPS, and the success orfailure of the system is dependent on them. However, the credit for the successof a TPS is often given to the information technology. Similarly, if the systemfails, it is reported as a ‘computer error’ even when the error is human, such asentering the wrong data.

• People from the environment are becoming participants in real-time pro-cessing systems as they directly enter transactions and perform validation. Forexample, when you withdraw money from an ATM, you are the participant ofa TPS. The transaction is performed using real-time processing. You enter thedata, such as account number, PIN and withdrawal amount.You also check andvalidate the data at the ATM.

IITT FFaaccttIT FactA transaction-processing designer (TP designer) is a person with theresponsibility for translating business requirements into a TPS that willsupport the business.

Examples of real-time transaction processingThree examples of real-time transaction processing are reservation systems, POSterminals and library loan systems.

Reservation systemsReservation systems are used extensively in any type of business involved insetting aside a service or product for a customer to use at a future time. They arecommonly used for people who are travelling, such as making a motel reservationor booking a seat on a train. These systems require an acceptable response timebecause the transactions are made in the presence of the customers. Somereservation systems automate decision-making functions, such as finding the flightthat best meets the customer’s needs. The steps for a typical motel reservationsystem are as follows:1 Answer customer enquiries about room availability and pricing for a certain

period.2 Place a reservation on one or more rooms and receive confirmation of that

reservation.3 Perform a cancellation of a reservation.4 Take up the reservation on arrival.5 Close off a customer’s account at the end of the stay and provide an invoice.6 Perform consolidation activities, such as a ‘night audit’ in which transactions

for the day are posted to the general ledger.7 Provide a report and information management functions.


The motel reservation system is a TPS. It consists of participants, data/information and information technology (see Figure 4.4). Steps 1 to 5 require real-time processing and are known as the ‘front office’ functions. Steps 6 and 7 are notso critical and are known as the ‘back office’ functions. In most reservation systems,the ‘front office’ is taken off line when the night audit is taking place.The night audit performs such tasks as backing up the reservations database,posting completed occupancy settlement transactions to the general ledger,executing periodic reports, and updating the data used for occupancy calcu-lations.The night audit is normally performed during the quiet business period, such asbetween 1.00 a.m. and 3.00 a.m. Periodic reporting functions, such as costingreports and occupancy reports, are scheduled during a night audit as they only needto be run infrequently. The night audit is often done using batch processing.

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Purpose• Sell a room and other services



• Collect customer details

• Update transactions

• Search database

• Display room information

• Motel staff

• Manager

• Confirmation

• Customer account

• Receipt/reports

• Room details

• Personal computer

• DBMS

• EFTPOS


Information System

Figure 4.4 Motel reservation system.

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Purpose• Sell goods and services



• Scan product

• Search database

• Update product inventory

• Display product information

• Store staff

• Computingpersonnel

• Barcode

• Product details

Information System

• Receipt

• POS terminal

• Central computer

• Barcode reader


Figure 4.5 POS system.

One of the advantages of a POS terminal is that the correct price of theproduct is received once the product number is entered. The product number isusually entered using the barcodes on the product. Barcode readers are used toread the barcodes and identify the product. Once the product is identified, thePOS terminal can provide the price and any other relevant information about the product (see Figure 4.6).

Point-of-sale terminalsPOS terminals are used by retail stores to sell goods and services (see Figure 4.5).In large retail organisations, POS terminals send inventory data to a centralcomputer when the sale is made. The central computer is usually a mainframe ormid-range computer that does the processing for the entire chain. If the POSterminal immediately processes the transaction data, it minimises the costs ofbatch handling. To accomplish this centralised processing of the transaction data,the data is converted to a form that can be easily transmitted through acommunication system.


Library loan systemA library loan system is used tokeep track of items borrowed fromthe library.When a person borrowsa book, the librarian scans thebarcode on the person’s member-ship card and the barcode on thebook. This information and thedate are immediately recorded onthe library database. The libraryloan system completes each trans-action in real time. (See Figure 4.7.)

A library loan system has manysimilarities with a reservation sys-tem. Its operational activities aresimilar and involve keeping infor-mation on products, their avail-abilities, usage and maintenance. Italso shares the concepts of a ‘frontoffice’ and a ‘back office’ in whichactivities are similar to areservation system. The onlysignificant difference is that thelibrary loan system has a larger number of items compared to the reservationsystem.These items are often stored in a special database called a data warehouse.

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ServerUPC

UPCUP

C/qu

antity

UPC/quantityPrice

Customerreceipt

Inventorydatabase

MIS

Purchasedatabase

Inventoryreport

Product database

POS system

Figure 4.6 System flowchart for a POS system.

Figure 4.7 A library loan system.

124 Options

Examples of batch transaction processingThree examples of batch transaction processing are cheque clearance, billgeneration and credit card transactions.

Cheque clearanceA cheque is a written order asking the bank to pay a certain amount of money toa particular person. When a cheque is issued to a person, he or she deposits it intoa bank account. However, the money cannot be withdrawn until the cheque hasbeen cleared. Cheque clearance involves checking that the person who wrote thecheque has enough money in his or her account to cover the cheque. It usuallytakes three working days. The cheques are cleared as a group during the bank’squiet period of the day. Cheque clearance involves batch processing.

Bill generationOrganisations create a bill, or invoice, for goods or services that have beensupplied to a customer (see Figure 4.8). They usually generate a group of bills ata scheduled time. This enables the user to effectively manage his or her time and results in less disruption to the main database. Bill generation is not doneimmediately but as a group.

Figure 4.8 Invoice.

BQMblast quarry maintenance

11 July 2000 TAX INVOICEPeter CIANCIOSI trading as BQM Milestone Mining ServicesMobile: 0414 00 44 22 24 Green Street

WOODSTOCK VIC 3751

ABN: 02 089466 721 Invoice Number: PC00015

Date Work Carried Out Hrs@$28 p/hr Plus GST

05-07-00 Workshop 3 $0084.00 $0092.40XM-0515 Exhibition Centre Filters 5 $0140.00 $0154.00

06-07-00 XP-0879 Gauges Frankston 1 $0028.00 $0030.80Change over Filters 2 $0056.00 $0061.60Delivered Springs - EyeWise Eppalock 2 $0056.00 $0061.60Workshop 3 $0084.00 $0092.40

07-07-00 Workshop 5 $0140.00 $0154.00Delivered Toggle - EyeWise Eppalock 5 $0140.00 $0154.00

TOTAL HOURS 26Hrs $3728.00 $3800.80

(GST inc.)


Credit card sales transactionsCredit cards have become an important method of paying for goods and services.Millions of such credit card sales transactions are completed every day. Some are done at POS terminals, and some are done by taking an impression of thecustomer’s credit card on a multi-page credit slip, which is then filled in by thesales clerk. The retailer sends the credit slips to the bank in a group and does notsend each credit slip individually. Similarly, the POS credit card sales transactionsare not processed immediately but are stored for later processing. In either case,credit card sales transactions are processed as a batch. Customers may view creditcard sales transactions, particularly those done at a POS terminal, as real-timeprocessing; but the actual updating is processed in a batch.

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1 Explain the difference between users and participants in the context of a TPS.

2 How are people from the environment becoming participants of a TPS?

3 Describe the steps for a typical motel reservation system.

4 Outline one advantage of a POS system.

5 Describe the procedures for a library loan system.

6 Compare and contrast a library loan system and a reservation system.

7 Describe the procedures for cheque clearance.

8 Why is bill generation done in a batch?

9 Describe the processing carried out in credit card sales transactions.

LEARNING ACTIVITIES

1 Real-time transaction processing systems perform information processes requiringparticipants, data/information and information technology. Clearly identify theparticipants, data/information, information technology and purpose of thefollowing TPSs:a reservation systemsb point-of-sale terminalsc library loan system.

2 Batch transaction processing systems perform information processes requiringparticipants, data/information and information technology. Clearly identify theparticipants, data/information, information technology and purpose of thefollowing TPSs:a cheque clearanceb bill generationc credit card sales transactions.

3 Describe the relationship between participants, data/information and informationtechnology for a POS system.

4 Construct a data flow diagram and a system flowchart to represent the followingTPSs:a library loan systemb credit card sales transactions.

Exercise 4.2

126 Options

4.3 Storing and retrievingA TPS requires an efficient method for the storage and retrieval of data. Data isstored in a database or a data warehouse. The data storage system requires well-designed backup and recovery procedures.

Databases and filesThe information processes in any large organisation are often unique and com-plex.The storage and retrieval of data must occur accurately many times each day.Storage and retrieval depend on databases and files.

A database is an organised collection of data. An organisation stores allaccounting and operational records in a database, often called an operationaldatabase. This database is a model of the organisation’s operational aspects. Thedata in an operational database is defined in a schema. The TPS usually has arestricted view of the operational database. For example, there is no need for anorder entry system to have access to the accounts payable data. This restrictedview, or subset, of the data is called a subschema. Databases are designed using ahierarchical, network or relational structure (see Figure 4.9).• A hierarchical database organises data in a series of levels. It uses a top-down

structure consisting of nodes and branches. Each node can have many branches,but each lower-level node (child) is linked to only one higher-level node(parent).

• A network database organises data as a series of nodes linked by branches. Eachnode can have many branches, and each lower-level node (child) may be linkedto more than one higher-level node (parent).

• A relational database organises data using a series of related tables. Relation-ships are built between the tables to provide a flexible way of manipulatingand combining data.

Network structure Relational structureHierarchical structure

Figure 4.9 Hierarchical, network and relational structures.


When designing a database for real-time transaction processing, the followingfeatures are important:• Good data placement. A large number of users are simultaneously performing

transactions to change data.The database should be designed to access patternsof data use and to place frequently accessed data together.

• Short transactions. Keeping transactions short enables the entire transaction tobe processed quickly, which improves concurrency. User interaction duringtransaction processing should be avoided as this slows down the system.

• Real-time backup. Real-time processing is characterised by continuous oper-ations with downtime kept to an absolute minimum. Backing up the databaseneeds to be scheduled during times of low activity to minimise effects on users.

• High normalisation. Redundant information is kept to a minimum when-ever possible to increase the speed of updates and improve concurrency.Reducing data also improves the speed of backups because less data needs tobe backed up.

• Archiving of historical data. Data that is rarely referenced should be archivedinto separate databases or moved out of the heavily updated tables. This keepstables as small as possible, improving backup times and query performance.

• Good hardware configuration. The hardware needs to be able to handle a largenumber of concurrent users and to provide quick response times.A file is a block of data. In a database, a file is divided into a set of related

records. The records contain the specific information, such as details about acustomer or a product. Every TPS uses files to store and organise its transactiondata. Batch transaction processing and real-time transaction processing requiredifferent types of files and different methods of storage and retrieval. In a TPS,there are five basic types of files:• A master file contains information about an organisation’s business situation.

The master file stores the operational database.Transaction data is stored in themaster file.

• A transaction file is a collection of transaction records. The data in thetransaction file is used to update the master file. Transaction files also serve asaudit trails and history for the organisation.

• A report file contains data that has been formatted for presentation to a user.• A work file is a temporary file in the system used during the processing.• A program file contains instructions for the processing of data. It is created

from a high-level programming language, such as Cobol, Fortran, Visual Basicor C++.

Data warehousingA data warehouse is a database that collects information from different datasources. Data gathered in real-time transactions can be used for analysis in anefficient manner if it is stored in a data warehouse.A data warehouse provides datathat is consolidated, subject-oriented, historical and read-only:• Consolidated. Data is organised using consistent naming conventions,

measurements, attributes and semantics. Organisations can use similar data indifferent formats. For example, true or false data can be represented asone/zero, on/off, true/false, or positive/negative. Data in the data warehouse isstored in a single, acceptable format. Data warehousing allows data from acrossthe organisation to be effectively used in a consistent manner.

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128 Options

• Subject-oriented. A large amount of data is stored across an organisation. Someof this data is irrelevant for executive reporting and makes querying the datadifficult. A data warehouse organises only the key business information fromoperational sources so that it is available for analysis.

• Historical. Real-time transaction processing systems represent the currentvalue at any moment in time for various aspects of the business, such as thestock inventory. They do not show the inventory at some time in the past.Querying the stock inventory a moment later may return a different response.However, data stored in a data warehouse is accurate for a specific moment intime, as it represents historical information and cannot change. The datawarehouse stores a series of snapshots of an organisation’s operational datagenerated over a long period of time.

• Read-only. After data has been moved to the data warehouse successfully, itdoes not change unless the data was incorrect. The data stored in a datawarehouse represents a particular point in time; it must never be updated.Deletes, inserts, and updates are not applicable in a data warehouse. The onlyoperations that occur in a data warehouse are loading and querying data.

Backup proceduresOrganisations have become very dependent on their TPSs. For example, making areservation when the computerised reservation system is down is often impossible.A breakdown in the TPS may stop the business. Well-designed backup andrecovery procedures minimise disruptions when the TPS goes down (see Figure4.10). A backup is another copy of the data that could be used to rebuild thesystem. If the system goes down, the recovery process rebuilds the system. Thesuccess of backup and recovery depends on implementing appropriate procedures.Backups are usually stored offsite or stored onsite in a fireproof safe.

Users

Processtransaction

Performbackup

Performrecovery

Masterfile

Transactiondata

Transactiondata

Database

Database

Database

Updateddatabase

Data tocomplete

transaction Transactiondata

Transactiondata sincelast backup

Transactionfile

Backupfile

Figure 4.10 A DFD showing backup and recovery.


Recovery processA TPS may fail for a number of reasons, such as system failure, human error,hardware failure, incorrect or invalid data, program errors, computer viruses ornatural disasters.To cope with failures, the TPS must be able to detect and correcterrors. The recovery of a database involves the backup, journal, checkpoint andrecovery manager:• Backup. Periodic backup copies are made of the entire database. Typically, a

backup copy is produced at least once a day. The copy should be stored in asecure location where it is protected from loss or damage.

• Journal. Journals maintain an audit trail of transactions and database changes.There are two basic journals, or logs. First, there is the transaction log. It recordsall the essential data for each transaction, such as data values, time oftransaction and terminal number. The second kind of journal is the databasechange log. It contains before and after copies of records that have beenmodified by transactions.

• Checkpoint. The DBMS periodically suspends all processing to synchronise itsfiles and journals. All transactions in progress are completed, and the journalentries are updated. The system is then said to be in a ‘quiet state’; and thedatabase, together with the transaction logs, is synchronised. The DBMS thenwrites a special record to the transaction file. This special record is called the‘checkpoint record’. The checkpoint record contains information necessary torestart the system. A copy of the database up to the checkpoint record isknown as a ‘checkpoint copy’. Checkpoints should be taken frequently, suchas several times an hour. When failures do occur, it is often possible to resumeprocessing from the most recent checkpoint with only a few minutes ofprocessing work to be repeated.

• Recovery manager. This is a program that restores the database to a correctcondition and restarts the transaction processing.The type of recovery procedure that is used in a given situation depends on the

nature of the failure. The general procedure involves restoring the data collectedfrom a backup device and running the transaction processing again.The two typesof recovery are backward recovery and forward recovery:• Backward recovery is used to back out or undo unwanted changes to the

database. It is used to reverse the changes made by transactions that haveaborted. For example, a bank transaction involved transferring $100 betweentwo different accounts. However, failure occurred after the $100 wassubtracted from one account but before it was deposited to the requiredaccount. Backward recovery involves the recovery manager restoring the firstaccount to its original value.

• Forward recovery starts with a backup copy of the database. It then reprocessesthe transactions in the transaction journal that occurred between the time thebackup was made and the present time. Forward recovery is much faster andmore accurate than backward recovery. Backward recovery involves the logic ofreprocessing each transaction, and this is very time consuming.

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Magnetic tapeMagnetic tape is often used as a backup medium.It can store large quantities of data inexpensively.Magnetic tape is a very long, thin strip of plastic,coated with a thin layer of magnetic material.Thetape is often wound on two reels inside acartridge. Tape is read from and written to using atape drive that winds the tape from one reel tothe other reel, causing it to pass a read/write head.The main disadvantage with magnetic tape is thatit uses sequential access to retrieve data. Thisform of access starts at the beginning of the tapeand reads all of the data until the required item isfound. Sequential access to data is slow, butmagnetic tape is a suitable medium for backup.Magnetic tapes have a variety of sizes and formats,such QIC tapes, DAT cartridges and 8-mmcartridges. (See Figure 4.11.)

Grandfather-father-sonGrandfather-father-son is a backup procedure that refers to at least threegenerations of backup master files. The most recent backup is the son, the secondlast is the father, and the oldest is the grandfather. Grandfather-father-son iscommonly used with magnetic tape for a batch transaction processing system. Iffailure occurs during a batch run, the master file is recreated by using the sonbackup and restarting the batch run. This backup is one generation from themaster file. However, if the son backup is destroyed or corrupted, it is necessary togo back another generation and use the previous backup (father). This process ofkeeping several generations of backup files ensures that the data can be recreatedand not lost. Organisations often keep more than three generations. For example,banks generally keep up to twenty generations.

Partial backupsPartial backups occur when only parts of the master file are backed up. Themaster file is usually backed up to magnetic tape at regular intervals, such asweekly or monthly. Transactions completed since the last backup are storedseparately and are called journals, or journal files. In the event of an accident, themaster file can be recreated from the backup tape and the journal files.

Updating in a batchBatch transaction processing collects the transaction data as a group, or batch, andprocesses it later. It has a time delay. Updating in a batch is used when transactionsare recorded onto paper (such as credit card slips) or stored on a magnetic tape.Transactions are collected and updated in a batch when it is convenient oreconomical to process them. Historically, updating in a batch was the only feasiblemethod when transaction details were stored on punch cards or magnetic tape.The information technology did not exist to allow the immediate processing oftransaction data.

Figure 4.11 Magnetic tapes.


There are two stages in batch processing. The first stage is the collecting andstorage of the transaction data in a transaction file. It involves sorting the data into sequential order. The second stage is the processing of the data byupdating the master file. This is not always a simple process. The updating of themaster file may involve data additions, updates and deletions that need to happenin a certain order. If one error occurs inthe batch, then the entire batch isrejected (see Figure 4.12).

Updating in a batch involvessequential access. Sequential accessoccurs when data is accessed in asequence. It is the only method ofaccessing data stored on magnetic tape.The steps in a batch update involveretrieving the transaction data from amagnetic tape. A batch update starts atthe beginning of the magnetic tape andreads all of the data in the order it wasstored. It is a time-consuming process tolocate a specific transaction on magnetictape. All previous transactions need to beexamined.

The information technology in abatch transaction processing systemrequires a secondary storage medium thatcan store large quantities of datainexpensively. Magnetic tape isfrequently chosen for these reasons. Thesoftware used to collect the transactiondata does not have to be online; and, ifnecessary, the user interface can bemodified to suit the specific application.

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Data entry

Daily transactions

Transaction file

Batch run

Update

Master file

Figure 4.12 Batch transaction processing.

132 Options

Updating in real timeReal-time transaction processing is the immediate processing of data. It providesinstant confirmation of a transaction. Real-time processing involves a largenumber of users who are simultaneously performing transactions to change data.It has resulted from recent advances in technology. Increases in the speed of datatransmission and improvements in bandwidth have made real-time transactionprocessing possible.The steps in a real-time update involve sending the transactiondata to an online database in a master file (see Figure 4.13). The person providingthe information is typically available to help with error correction and receivesconfirmation of transaction completion.

Data is accessed from a real-time transaction processing system using directaccess or random access. Direct access occurs when data is accessed withoutaccessing previous data items. It is much faster than sequential access, as theprevious data is not read. A direct access storage device stores data in a particularstorage location based on a mathematical procedure, or algorithm. It uses thisalgorithm to calculate the approximate location of the data. If the data is notfound at this location, it searches through successive locations until the desireddata is accessed. Direct access often involves the use of an index and is calledindexed access.An index is a table that contains information about the location ofthe data.

The information technology in a real-time transaction processing systemrequires a secondary storage medium that can store large quantities of data andprovide quick access. Magnetic disk storage was developed to provide immediateaccess to data. The software used to collect transaction data is online and has a

Data entryUpdate

Daily transactions

Transaction file Master file

Transaction data

Figure 4.13 Real-time transaction processing.


user-friendly interface. The interface is very important, as a rapid response time iscritical. The turnaround time from the input of the transaction to the productionof the output must be a few seconds or less.

133

1 Explain the difference between hierarchical, network and relational databases.

2 List six important features in the design of a database for real-time transactionprocessing.

3 Describe five file types used in a TPS.

4 What is the purpose of a transaction file?

5 Describe the features of consolidated data in a data warehouse.

6 ‘Data stored in a data warehouse is accurate as it represents historical infor-mation.’ Explain this statement.

7 What is a backup?

8 Explain the difference between a transaction log and a database change log.

9 What is a checkpoint in the recovery process?

10 Explain the difference between backward recovery and forward recovery.

11 Why is magnetic tape often used as a backup medium?

12 Describe the process of using generations of backup master files for recovery.

13 What are the two stages in batch processing?

14 Describe updating in a batch that involves sequential access.

15 What are the steps in a real-time update?

16 Describe direct access of data from a real-time transaction processing system.

LEARNING ACTIVITIES

1 Relational databases are used for TPSs. They organise data using a series of relatedtables. Briefly describe the following terms: schema, entity, attribute, relationship,table and form.

2 The entertainment centre has set up a reservation system for all its events. Thesystem uses a relational database. There are three entities: Customer, Seats, andEvents.– Customer: CustomerID, LastName, FirstName, Address, Suburb, PostCode,

Deposit and CreditCard.– Seats: SeatNumber, EventID and CustomerID.– Events: EventID, EventTitle, Date and Time.a What would the primary key be for each entity?b Create a data dictionary for this relational database.c Create a schematic diagram for this relational database.d Design a form for each entity that could be used for data entry.e Populate the database with dummy data.f Create four queries that would be relevant to this database.g Create a report that lists all the customers and their seat numbers for a par-

ticular event. The report should be sorted on seat number in descending order.h Apply backup and recovery procedures to protect this data.

Exercise 4.3

134 Options

4.4 Other information processesAll information processes play a role in a TPS, including collecting and analysingdata.

CollectingCollecting data for a TPS involves generating the transaction data. For example,people using an ATM generate transaction data by entering their debit cardnumbers and typing their requests on a keyboard. Collecting in transactionprocessing involves the use of hardware and a variety of forms.

HardwareHardware used to collect data for a TPS includes MICR readers, ATMs andbarcode readers.

MICR (magnetic ink character recognition, pronounced ‘my-ker’) systems are widely used by banks to read account numbers on cheques (see Figure 4.14).Characters are printed using magnetic ink that contains magnetised particles.

3 A relational database is used for a library loan system. There are three entities:Book, Borrower and Transaction.a List the attributes needed for each entity.b Create a data dictionary for this relational database.c Create a schematic diagram for this relational database.d Design a form for each entity that could be used for data entry.e Populate the database with dummy data.f Create four queries that would be relevant to this database.g Create a report that lists all the transactions on a particular date.h Apply backup and recovery procedures to protect this data.

Figure 4.14 Cheque with MICR.


MICR systems are designed to quickly and accurately read prerecorded data oncheques and deposit slips. A MICR reader processes cheques at speeds of up to2000 cheques per minute. The use of MICR for reading cheques is an example ofa batch transaction processing system.

An ATM (automatic teller machine) is a banking terminal that performscommon banking transactions, such as deposits and withdrawals. An ATM can beused at any time during the day or night. When people complete a transactionusing an ATM, they are participants in a real-time transaction processing sys-tem. The ATM accesses a communication system. Data and information are being transferred between an ATM terminal and the bank’s central computer in real time.

Barcode readers are used extensively in retail industries to collect productinformation at point of sale. Supermarkets use a laser to read barcodes (see Figure4.15), and many businesses use handheld barcode readers. Product information(description, price and code) is held on a central computer linked to the POSterminal. Data about the item passing the barcode reader is collected quickly andaccurately. The description and price of the item is displayed on the cash registerand printed on the receipt. Libraries and many industries use barcode readers tokeep track of stock movements.

135

FormsA form is a document used to collect data from a person. When the form iscompleted, it is processed in a batch or in real time.

There are many different types of paper forms, such as a sign-on sheet forpayroll. A person completes the paper form, and the form is processed as a batchat a convenient time. (See Figure 4.16.)

Figure 4.15 Barcode reader in use.

136 Options

On-screen forms are created for computerised data entry purposes to populatefields in a database. The user can view, enter and change data in real time. (SeeFigure 4.17.) For example, an airline ticket reservation system collects details of acustomer’s required flight via a form. A transaction is completed when the usercompletes the form. A well-designed form provides information explaining the

Figure 4.16 A Medicare form.

Requiredinputs

Verificationinformationfrom system

Reservation code

Book code

Book title

Reserved date

Student ID

Student name

OK Cancel

[10123]

[USING MEDIAGRAM]

[AVRIL STARK]

005-3001.01

03/01/00

1710GLB

Figure 4.17 Data entry.


required data and any rules that apply to particular fields, such as Sex (M/F).Forms can minimise data entry errors by automatically filling in previously storeddata, such as a customer’s address, once the user has entered the customer’s name.

Web forms are typically used by users who wish to purchase items over theInternet (see Figure 4.18). A form on a Web page may request relevant data, suchas items to be purchased, delivery address and method of payment.The data froma Web form may be processed immediately (real-time processing) or at a latertime in a group of Web forms (batch processing). The responses from a Web formbecome data in fields of a database.

137

Figure 4.18 Web form.

Analysing dataThe results of processing transactions are stored in a database and are analysed inmany ways to meet the information needs of users.That is, the output from a TPSis the input to other types of information systems, such as decision supportsystems and management information systems.

Decision support systemsTPSs flow through all aspects of an organisation and can provide the informationnecessary to make informed decisions. Decision support systems (DSSs) assistpeople to make decisions by providing information, models and analysis tools. Forexample, a business uses a TPS to process its sales transactions. It uses a databaseas a DSS to periodically summarise its sales data by date, region and product.Thissummary information is stored in a separate database to be analysed by seniormanagement. To make decisions, management needs to be able to determinetrends in sales quickly by querying the data based on various criteria.

The amount of information available from TPSs is increasing at a staggeringrate. It has reached the point where people are being frustrated by information

overload. Data mining is used in DSSs to find relationships and patterns in thedata stored in a database. It sorts through the data and turns up interesting andoften useful connections. For example, data mining could be used to analyse thetransactions at the supermarket. It might determine whether there was arelationship between tomato sauce sales and meat pie sales. This informationmight be useful for marketing promotions. The information obtained from datamining allows organisations to make more informed decisions about such topics asimproving marketing campaigns or siting a new store.

IITT FFaaccttIT FactCICS (customer information control system, pronounced ‘kicks’) is a main-frame operating environment designed to enable transactions entered atterminals to be processed concurrently.

Management information systemsManagement information systems (MISs) provide information for the organi-sation’s managers. They present basic facts about the performance of theorganisation. Some common examples of MIS output are reports on sales,stock inventory, payroll, orders and budgets. Information from an MIS is gen-erally presented in report form. There are many different types of reports, such as scheduled reports, forecasting reports, on-demand reports and exceptionreports:• Scheduled reports are standard reports provided on a regular basis. Middle-

level to low-level management uses these reports.• Forecasting reports are used to help make projections about business trends.

These reports are important to the decision-making process. They are alsoknown as planning reports as they assist in the strategic planning of theorganisation. High-level management normally uses these reports.

• On-demand reports are generated on request and usually in response to aspecific need. They are generally requested by high-level management.

• Exception reports are used to alert management to unexpected or un-favourable situations that necessitate special handling.This type of reporting isof interest to middle management.The development of MISs and DSSs brought operations researchers and indus-

trial engineers to the forefront of business planning. These information systemsrequire knowledge of an organisation and its activities in addition to technicalskills in computer programming and data handling. The key issues in designing anMIS or a DSS include how a system will be modelled, how the model of thesystem will be handled by the computer, what data will be used, and how far intothe future trends will be extrapolated.

138 Options


4.5 Issues related to transactionprocessing systemsBoth positive and negative impacts arise from the use of a TPS. In this section, weexamine some of the issues raised by TPSs, such as the nature of work, non-computer procedures, bias, the importance of data, and control in transactionprocessing.

Nature of workTPSs are changing the nature of work for many people.They essentially automatebusiness operations and hence will affect the people who perform theseoperations. The automation of jobs and people from the environment completingthe transaction have affected the nature of work in many organisations.

Automation of jobsAutomation of jobs refers to the use of information technology to perform tasksonce performed by people. For example, the POS terminal has replaced many ofthe tasks performed by people in a manual transaction system, such as memorising

139

1 What are the advantages of using a MICR system?

2 Describe an ATM.

3 How are barcode readers used in retail industries?

4 What is an on-screen form?

5 How can forms minimise data entry?

6 Describe a Web form.

7 What is a decision support system?

8 What is the purpose of data mining?

9 Describe four types of reports used in management information systems.

10 What are the key issues in designing an MIS or a DSS?

LEARNING ACTIVITIES

1 A range of hardware devices is used in TPSs. Clearly describe the operation of thefollowing devices to collect data:a ATMb barcode readers.

2 Identify and collect three paper forms used in a TPS. Compare and contrast thedesign of these forms. Will these paper forms be replaced by electronic versions inthe future? Give reasons for your answer.

3 Design a user-friendly form that could be used in a real-time transaction pro-cessing system, such as an airline reservation system. Describe the features thatmake your form user-friendly.

4 Search the Internet for Web forms that would be used in a TPS. List the address ofthree Web forms that follow good design principles. Compare your choices withthree students in the class. Determine the best Web form in your group.

Exercise 4.4

140 Options

the price of products. Organisations are increasing their use of informationtechnology and TPSs. TPSs have allowed organisations to be more efficient andoffer a range of new services. However, they have contributed to many of thechanges in the workplace. Workers are required to learn new skills and completeongoing training. The automation of jobs often results in fewer people beingrequired to perform the same task. However, the loss of jobs in one industry isoften replaced by the job growth in another industry, such as the informationtechnology industry.The key ingredient is being retrained to perform new roles inthis growing industry.

People as participantsPeople from the environment have becomeparticipants in TPSs as they directly entertransactions. For example, when a personwithdraws money from an ATM, he or she isthe participant of a TPS (see Figure 4.19). Theeffect of this change on the nature of work issignificant. An employee of the bank oncecarried out the tasks completed by a person atthe ATM. This has resulted in fewer jobs inbanks. This issue is not restricted to banks. TheInternet is allowing people to becomeparticipants in a range of TPSs. People arepurchasing an increasing range of products bycompleting a Web form. They are bypassing arange of people who provided this service atthe shop front. On the other hand, moreopportunities are being created in theinformation technology industry to create thisuser interface.

Non-computer proceduresMany organisations rely heavily on their TPS. When the computer is unavailabledue to a breakdown or other reason, non-computer procedures are needed to dealwith transactions in real time. For example, if the library loan system crashes, thenthe librarian needs to have a non-computer procedure for customers to borrow abook.When the computerised system is working again, the user needs a procedureto enter the transactions completed by non-computer procedures.

BiasData needs to be free from bias. Bias means that the data is unfairly skewed orgives too much weight to a particular result. It is rarely an issue in the collection

Figure 4.19 People as participants.


of data from a TPS, such as a POS terminal. This information process is carefullydesigned and examined in many ways. However, the data gathered from a TPS canbe presented in a biased way using tables and charts. For example, tables can beconstructed without all the relevant data, and scales on charts can distort trends.Some bias may exist in any explanation; however, it becomes an ethical issuewhen the relevant information is knowingly misrepresented.

Importance of dataAn organisation relies on its TPS and the data it processes. It is important fororganisations to have procedures in place to ensure that data is secure, accurate and valid.

Data securityData security involves a series of safeguards to protect the data. Data is underthreat of being stolen, destroyed or maliciously modified. There is a greater riskwhen the data is accessible to multiple users in a real-time transaction processingsystem. The first line of defence is to only allow access to data to authorisedpeople using passwords, personal objects and biometric devices. However, somepeople are capable of evading these procedures. Further safeguards to protect datainvolve data encryption and firewalls.• Encryption is the process of coding data, and decryption is the process of

changing it back. It is the most effective way to achieve data security duringthe transmission of data. Data is coded, transmitted, and then converted backto its original form.

• Firewalls are used on networks to verify and authenticate all incoming data.A firewall checks the password of anyone trying to access a network. Firewallsare expensive to install and maintain. On large systems, more than one firewallis necessary because barriers need to be placed at all critical points.

Data accuracyAccuracy of data is the extent to which it isfree from errors. Data entered into a TPS isnot always accurate. Errors can be caused bymistakes in gathering the data, mistakes indata entry, a mismatch of the data and theperson, or out-of-date information. Forexample, if the price of a product has beenentered incorrectly into the database, thencustomers buying that product will becharged the wrong price. This could be verycostly to the organisation. Opportunitiesneed to exist to check and change data if it iswrong.

141

142 Options

Data validation is used to check the entry of data. A well-designed TPS checkseach transaction for easily detectable errors, such as missing data, data values thatare obviously too high or too low, data values that are inconsistent with other datain the database, and data in the wrong format. Data validation is carried out usingrange checks, list checks, type checks and check digits as discussed in Chapter 2.

Data integrityData integrity describes the reliability of the data. It involves the accuracy,currency and relevance of the data. Data integrity in real-time transactionprocessing is provided when the transaction passes the ACID (atomicity,consistency, isolation and durability) test.• Atomicity occurs when all of the steps involved in a transaction are completed

successfully as a group. If any step fails, no other step should be completed. Ifthe first step succeeds, then the second step must succeed; otherwise, the entiretransaction is abandoned. If some operations succeed and others fail, there is noatomicity.

• Consistency occurs when a transaction successfully transforms the system andthe database from one valid state to another. Consistency in a TPS stems fromthe correct application programming, such as always debiting and crediting thesame amount.

• Isolation occurs if a transaction is processed concurrently with other trans-actions and still behaves as if it were the only transaction executing the system.Transactions must not interfere with each other’s database updates.

• Durability occurs if all the changes that a transaction makes to the databasebecome permanent when the transaction is committed.These ACID properties guarantee that a transaction is never incomplete, the

data is never inconsistent, concurrent transactions are independent, and the effectsof a transaction are permanent.

IITT FFaaccttIT Fact‘Acid test’ comes from the days when alchemists subjected metal samples tostrong acid to isolate the gold content. Today, it refers to rigorous testing.

Control in transaction processingControlling transaction processing starts with collecting and includes the way theTPS manipulates the data and the way errors are corrected. Data preparation andauthorisation create the transaction data that will be entered into the TPS. Peoplein management positions of some organisations have created false transaction datato promote their careers. Even though strict precautions are taken with datapreparation and authorisation, the results from a TPS are not always correct.People should not become completely dependent on a TPS.They need to maintaincontrol over their organisation’s operations.

Transaction processing systems 143

1 What is the automation of jobs?

2 Describe some of the changes in the workplace as a result of automation.

3 How is the Internet allowing people to become participants in a range of TPSs?

4 Why are non-computer procedures needed in a TPS?

5 How is bias a problem in a TPS?

6 Explain the difference between encryption and firewalls.

7 Describe some of the ways inaccurate data is entered into a TPS.

8 What is data integrity?

9 What is the purpose of the ACID text?

10 Outline the issue of control of data in a TPS.

LEARNING ACTIVITIES

1 Identify three jobs that have changed as a result of TPS. Describe the implicationsof these changes for participants of the system.

2 ‘The computerisation of transaction processing has resulted in people perform-ing menial tasks. People are now not required to think.’ Comment on thesestatements.

3 ‘The major concern for organisations in TPS is ensuring data is secure, accurate andvalid.’ Discuss this statement. Use the Internet to find information about datasecurity. Compare Australian and overseas data.

4 A friend has obtained access to a bank’s credit card transactions. Do you think your friend is clever? Has your friend committed a crime? What would you do if the friend deleted all your credit transactions for the past month? Describe thepenalty your friend should receive if he or she is caught.

Exercise 4.5

Chapter reviewPART A


1 Which of the following is not animportant characteristic of a TPS?A rapid responseB reliabilityC flexibilityD controlled processing

2 Batch transaction processing is used for:A generating pay chequesB making an airline reservationC buying a product at a point-of-sale

terminalD borrowing a book at the library

3 Real-time transaction processing:A has more errors than batch trans-

action processingB does not require continuous access to

the master fileC is more difficult to maintain than a

batch transaction processing systemD processes transactions in a group

4 Data compared to a set of accepteddata is called a:A range checkB list checkC type checkD check digit

5 Which of the following is not a featureof data in a data warehouse from a real-time transaction processing system?A a large amount of data is stored from

across an organisationB data is stored in a single, acceptable

formatC data is current and contains the latest

transaction dataD data does not change unless the data

was incorrect

6 A database that organises data using aseries of related tables is called a:A hierarchical databaseB relational databaseC operational databaseD network database

7 Updating in a batch usually involves:A sequential accessB an online databaseC direct accessD magnetic disk storage

8 Which of the following is not involvedin collecting data for a TPS?A ATMB MICRC POSD DSS

9 Which part of the ACID test ensuresthat all of the steps involved in atransaction are completed successfullyas a group?A atomicityB consistencyC isolationD durability

10 The issue of bias is raised:A during the collection of dataB to ensure people maintain control

over their organisation’s operationsC when data is gathered from a TPS

and presented using tables andcharts

D during the transmitting and receiv-ing of data

144 Options

Chapter review

Transaction processing systems 145

PART B


Statements

1 A database that collects informationfrom different data sources.

2 A copy of the data that could be usedto rebuild the system.

3 Collects, stores, modifies and retrievesthe transactions of an organisation.

4 Collects the transaction data as a groupand processes it later.

5 Involves the accuracy, currency andrelevance of the data.

6 Ensures that all of the steps involved ina transaction are completed successfullyas a group.

7 Ensures that two users cannot changethe same data.

8 Occurs when data is accessed withoutaccessing previous data items.

9 The immediate processing of data.

10 Used in DSSs to find relationships andpatterns in the data stored in a data-base.

11 Used to check the entry of transactiondata.

12 Maintains an audit trail of transactionsand database changes.

13 Occurs when data is accessed in asequence.

14 At least three generations of backupmaster files.

15 The use of information technology toperform tasks once performed bypeople.

16 The software that allows the trans-action processing application programsto run efficiently.

List of terms

a atomicity

b automation

c backup

d batch transaction processing

e concurrency

f data integrity

g data mining

h data validation

i data warehouse

j direct access

k grandfather-father-son

l journal

m real-time transaction processing

n sequential access

o transaction processing monitor

p transaction processing system

PART C


1 Outline the main differences betweenreal-time transaction processing andbatch transaction processing.

2 ‘Customers may view credit card salestransactions as real-time processing, butthe actual updating is processed in abatch.’ Comment on this statement.

3 Explain the meaning of the followingterms:a transactionb atomicityc grandfather-father-son.

4 Describe the backup and recovery pro-cedures for a TPS.

5 How is updating in a batch differentfrom updating in real time?

6 Data is important in a TPS. Briefly des-cribe some of the procedures used toensure that data is secure, accurate andvalidated.

7 Data integrity is provided when a trans-action passes the ACID text. Describethe four parts of the ACID test.

55DECISION SUPPORTSYSTEMS

cchhaapptteerr









Outcomes

This chapter examines the characteristics ofinformation systems that help users makedecisions. You will study examples of decisionsupport systems and learn to develop your own decision support systems. Decision supportsystems focus on the information processes oforganising, analysing and processing.

Overview

Decision support systems

5.1 Characteristics of decisionsupport systemsThe success of most human activities depends on the quality of the decisions.Decisions are needed whenever a problem needs to be solved. Decision supportsystems (DSSs) are information systems that assist users to make a decision byproviding information, models and analysis tools. They use a range of softwaretools, such as databases, spreadsheets and expert systems. DSSs help decision-making by providing information using a model. A model is a representation ofsome aspect of the real world, and a simulation is the use of that model. A modelmay be a formula for calculating the cost of a new product to make a profit. ADSS depends on the accuracy of the model.

147

A DSS can be used on a daily basis or when an organisation has to makechanges or react to something unexpected. One example of a DSS is a system thatanalyses the stock market and helps make decisions about shares. A DSS creates amathematical model of the variables affecting the decision, using statistical tools,databases, spreadsheets and graphics. The model allows a manager to ask what-ifquestions by changing one or more of the variables and seeing the projectedresults. For example, the manager might ask what would happen if the share pricewere raised.

Nature of decision support systemsThe interactive nature of DSSs and the ability of the user to ask appropriatequestions are important factors in a DSS. Interactivity allows the user to choosethe sequence and content of the information to be displayed. It allows a DSS tomake decisions based on the data entered by the user. For example, a managerwants to expand a business into a new product line. He or she enters the details ofthe business’s current operations and an estimate of the effect of the new productinto a DSS. The DSS provides the information to assist the manager to make thecorrect decision. The interactive nature of DSSs requires the user to have anunderstanding of analytical tasks. If the user does not ask the right questions, it isunlikely that the DSS will provide the right decision.

DSSs require the user to have an understanding of the problem and whetherusing a DSS is appropriate. For example, taking a holiday requires a number ofdecisions regarding time, place, transport, and accommodation (see Figure 5.1).The user needs to understand the problem and all the factors that have an effecton the decision. The difficulty of making a decision depends on the number ofconditions that have to be satisfied. A decision is easy to make when one option is

IITT FFaaccttIT Fact‘Wetware’ is the term computer scientists use to refer to the brain’sknowledge. Computer scientists are trying to find ways to connect humanbrains to computers, so people can directly interact with them.

148 Options

clearly better than another option. DSSs use three important informationprocesses:• collecting—gathering data, such as facts, beliefs and ideas, that are related to

the problem• organising—determining a method of organising data and selecting an

appropriate model• analysing—selecting a course of action based on the information provided in

the previous steps.

Figure 5.1 Taking a holiday trip requires a number of decisions.

Components of a decision support systemMost DSSs have three components: data management, model management anddialogue management (see Figure 5.2):• Data management is used to collect and organise the data. For example, stock-

brokers need access to share prices for past years. They use a database systemfor data management. It maintains the data and provides a means for selectingthe required information. A DSS is often linked to external databases that areused for other purposes, such as shipping, invoicing or daily transactions.

• Model management involves the use of a model to turn data into information.People establish the relationship between quantities based on what theyobserve and measure in real life. A model describes the relationship betweeninputs, outputs and conditions. Models must be built and tested. There aremany types of models depending on the application, such as accountingmodels to represent depreciation, tax planning or cost analysis. The validity ofthe information obtained from model management is dependent on theaccuracy of the model.

• Dialogue management allows the user to enter a request in a convenientmanner. It provides the interactivity of DSSs. Dialogue management helps the user to search large amounts of data, focus on relevant facts and apply a model.


Classifying situationsA DSS depends on the situation, the nature of data, the accuracy of the modeland the method of analysis. Situations are classified as structured, semi-structuredor unstructured.

Structured situationsStructured situations have decisions that are automated. The decision or solutionis reached using an algorithm. An algorithm is a series of steps that will solve theproblem in a finite time. In a structured situation, the steps are known and mustbe followed in a certain sequence. For example, calculating the amount of carpetneeded for a room is solved using an algorithm. It uses a parameter (or a value ofdata that may change), such as the width of the carpet or the dimensions of theroom. Structured situations always result in the same solution if the values of the parameters remain the same. DSSs are not required in structured situations.

Semi-structured situationsSemi-structured situations follow a method to reach a decision, but the correctdecision is not guaranteed. The requirements of a semi-structured situation areclear cut, but there are too many factors or some unknown factor that may affectthe decision. Experts in the fields of financial investment, weather prediction and

149

Data Management

Retrieves and manipulatesrelevant data

Model Management

Maintains alphanumericand graphical models,

formulas and algorithmsthat are often used toselect the best model

Dialogue Management

Input tools (icons andcommands) accept

inquiries

Presentation tools(tables and charts)present analysed

information

Figure 5.2 Components of a decision support system.

150 Options

horse racing believe that these are semi-structured situations. The experts’knowledge allows them to obtain a manageable number of alternative solutionsbut does not always result in the best solution. Some experts in a semi-structuredsituation may reach a completely different solution. Most real-world situations aresemi-structured and can use a DSS (see Figure 5.3).A semi-structured situation isa combination of a structured and an unstructured situation. It is neither clear cut like a structured situtation nor unpredictable like an unstructured situation.

Figure 5.3 Weather forecasting, stock investing and horse racing are examples of semi-structured decision-making.

Structured Problems Semi-structured ProblemsHow many workers are needed to fully What are the benefits of merging with staff this production line? XYZ Inc.?

What is our optimal order quantity for Where should we build the next five raw material, based on our production? stores of our retail chain?

How many turbines are needed to How will the consumer react if we lower supply power to this factory? the price of our product by 10%?

Which of our regions yields the highest What is the best advertisement revenue per salesperson? campaign to launch our new financial

service?

Which money market fund currently What are the benefits of opening an yields the highest return? office in Paris, France?

How much would the implementation Which stock will yield the highest of pollution-preventing devices cost us? return by the end of the year?

Table 5.1 Examples of structured and semi-structured problems.

Unstructured recognised situationsUnstructured recognised situations do not use a method to reach a decision.Theyrequire judgement and insight into the problem. In an unstructured situation,there is no algorithm to reach the best solution. There are too many factors or toolittle knowledge about the situation. For example, people who buy shares with noknowledge of financial investments are making a decision in an unstructuredsituation. It is unpredictable. If the people used a financial adviser, their decisionwould be based on a better judgement. However, the situation would still beunstructured unless the financial adviser followed a method to reach a decision. Inunstructured situations, there is no single method to reach a decision and noguarantee that the decision will be correct. It is dependent on intuition. DSSs areused for unstructured recognised situations.


Whether a situation is classified as semi-structured or unstructured depends onthe amount of knowledge and experience the user has in that area. For example,a meteorologist would regard predicting the chance of rain tomorrow as a semi-structured situation, while many people would regard it as unpredictable and anunstructured situation. The development of DSSs that use artificial intelligence,such as expert systems, have resulted in previously unstructured situations beingregarded as semi-structured situations.

151

1 What is a decision support system?

2 List three types of software tools used in a DSS.

3 What is a model?

4 Why is interactivity an important factor in a DSS?

5 List the three components of a DSS.

6 Explain the difference between data management and model management.

7 What is the purpose of dialogue management in a DSS?

8 Explain the difference between structured and unstructured situations.

9 Describe a structured situation.

10 What is a semi-structured situation?

11 Why isn’t an algorithm used in an unstructured situation?

LEARNING ACTIVITIES

1 A DSS is used by a manager to employee a secretary. Decisions are based onselection criteria, such as typing speed. List the criteria you would regard asrelevant for this DSS. How would you organise this data? Which criteria are themost important? How could the DSS make decisions based on this information?

2 Describe a marketing situation that would benefit by using a DSS. Outline theinformation technology needed by this system.

3 ‘The classification of situations into unstructured and semi-structured is dependenton the user of the DSS.’ Do you agree with this statement? Give reasons.

4 Describe two situations that you would classify as:a structuredb semi-structuredc unstructured.

5 Search the Internet for two examples of a decision support system. Describe thecharacteristics of these systems.

Exercise 5.1

152 Options

5.2 Examples of decision supportsystemsDSSs assist users in semi-structured and unstructured situations. They are notused in structured situations.

Semi-structured situationsMany decisions are made by people in semi-structured situations, such as a bankofficer deciding how much to lend a customer or a fingerprint expert doingfingerprint matching.

BankingBank officers are involved in approving loans. This is a semi-structured situation,as there are many different options for both the bank and the customer. The bankhas to assess the risk involved in lending the money. The bank officer collects dataabout the customer’s financial status, such as the customer’s income and expenses.The customer compares different types of loans and then makes a decision on themost suitable loan.

A bank officer enters all the relevant data into a DSS. A list of loan optionsallows the bank officer to compare different loans. The DSS assists by screeningthe applicants and helping the bank officer to make a consistent decision in linewith the bank’s lending policy. It also provides advice to the customer on anappropriate type of loan. Customers also have access to a range of software to analyse loans, such as the Home Loan Analyser. This DSS allows the user tocompare different home loans from any lender and accurately estimate the totalcost of the loan.

Fingerprint matchingAn automated fingerprint identification system(AFIS) is used to help fingerprint experts tomatch prints (see Figure 5.4). It is a databasesystem that is capable of matching prints andsearching at a rate of 2000 fingerprints persecond. An AFIS uses a combination of imageprocessing and matching algorithms to find amatch in a few seconds. Before AFISs, the manualidentification of fingerprints would have takenhours or even days. It was a labour-intensive task.Fingerprint experts had to be knowledgeable inall areas of fingerprint identification. Theyneeded extensive knowledge to compare printsand also had to know the procedures for locating,processing and preserving prints.

An AFIS still requires an expert, as the AFISgenerates a list of possible matches. However,advances in scanning, digital imaging andmatching algorithms have result in more accurate

Figure 5.4 Fingerprint.


AFISs. These advances have resulted in experts seeing themselves as little morethan technicians. However, fingerprint matching still requires an expert to witnessall phases of fingerprint identification. The expert is required to make a decisionand use judgement regarding the degree of similarity between two prints.

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Unstructured situationsPeople make many decisions in unstructured situations, such as predicting stockprices and managing disaster relief.

Predicting stock pricesDSSs are used to analyse stock prices and make decisions about shares.They oftenstore data on share prices in a database or a spreadsheet. DSSs use this data and amodel based on different parameters to predict future stock prices. Unfortunately,predicting stock prices is an unstructured situation and unforeseen events occur.A financial adviser may suggest certain shares to buy. However, this type of adviceis based on intuition and judgement. Financial advisers are usually very confidentabout their advice but will never guarantee their decisions. DSSs in this situationmake use of spreadsheets, databases and neural networks.

Managing disaster reliefA disaster is a sudden, usually unexpected, catastrophe. In Australia, disastersinclude fires, floods, earthquakes and cyclones. Disaster relief organisations res-pond after the diaster has occurred. They may use a geographic informationsystem (GIS). A GIS is an information system capable of assembling, storing,manipulating, and displaying geographically referenced information (see Figure5.5). It lets the user query or analyse a relational database and display the resultsin the form of a map. A GIS has many uses besides disaster relief management,such as weather forecasting, sales analysis and population forecasting. In a GIS, thegeographic information is described explicitly in terms of geographic coordinates,such as latitude or longitude, or implicitly in terms of a street address.

IITT FFaaccttIT FactThe NSW Police Fingerprint Section was established in 1903 with 6000 sets of fingerprints. Their automated fingerprint identification system wasestablished in 1986. It now uses a database containing 1.8 million sets offingerprints.

154 Options

Types of decision support systemsDSSs use a combination of spreadsheets, databases, expert systems and neuralnetworks to assist in decision-making.

SpreadsheetsA spreadsheet uses a rectangular grid made up of rows and columns to organiseand store data that requires some type of calculation. The results of thesecalculations are often displayed in charts for analysis. Business people were thefirst to use a spreadsheet to keep track of financial transactions and in stockcontrol. It allowed them to make decisions based on trends and to present data intables and charts. Today, spreadsheets are used by scientists, engineers and a widerange of other people to assist in decision-making.

A spreadsheet creates a model using formulas to represent the real situation.For example, a spreadsheet could be used to calculate loan repayments. It woulduse a formula that relates the interest rate, time period and present value of theloan. A spreadsheet helps with decision-making using a technique called ‘what-if’predictions. ‘What-if’ is the process of making changes to the data and observingtheir effects. For example, in the Best Books spreadsheet (see Figure 5.6), the usercould change the cost price and observe the effect on the profit.

The intersection of a row and a column in a spreadsheet is called a cell. Theposition of the cell in the spreadsheet is called its cell reference (or cell address).A range is a group of cells in a single row or column or in several adjacent rowsand columns. For example, the range B5 to C7 (written as B5:C7) contains thedata in cells B5, B6, B7, C5, C6, and C7.

A spreadsheet is very particular about the type of data that is entered into eachcell. It has three main types of data:• A label is text entered into a cell to provide some explanation of the

spreadsheet. Calculations are not carried out using this data. Labels are usedfor headings in rows and columns.

Digitising ofexisting maps

Multiple paperproducts

Translation ofexisting maps

Multiple digitalproducts

GIS

Cartographicdatabase

Figure 5.5 Components of a GIS.


• Values are numbers stored in a spreadsheet on which calculations are carriedout.

• Formulas are instructions to perform a calculation. The answer to thecalculation will always appear in the cell that contains the formula. Theformula itself is not shown. The user can create a formula or select a functionsuch as AVERAGE. IF statements are combined with functions to allowcomplex decision-making (see Figure 5.7).

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Figure 5.6 A spreadsheet for Best Books.

Spreadsheets have many features that make them easy to use and suitable for aDSS. Some of the features include editing data, workbooks, templates, macros and charts.• Editing data is completed on the spreadsheet or using the formula bar. Cut and

paste, copy and paste, or drag and drop features are used to copy values, labels,cell references and formulas into other cells. The ‘Fill Down’ or ‘Fill Right’commands copy the contents of a cell into a range of adjacent cells.

• A workbook is made up of one or more spreadsheets called worksheets orsheets. These sheets allow the user to organise related information in a singlefile.

• A template is a document created for repeated use. A spreadsheet templatecontains labels and formulas to solve a particular problem. The user enters thevalues to obtain the required solution. A template saves time and effort.

Figure 5.7 A spreadsheet for Mick’s Music.

= D6+E6

Label Value

Formula= SUM(G5:G10)

= E5–F5

= B5*C5

= C5*1.5 = B5*D5

= IF(AND(B6>10,C6>50),200,0)

= IF(OR(B6>10,C6>50),10*C6,0)

156 Options

• A macro is a series of commands stored in a file that can be executed bypressing a few keys. Macros allow many operations to be performed auto-matically, such as opening menus, choosing commands or entering text. Macrosare used to create the dialogue management component of a spreadsheet beingused as a DSS.

• A chart is a graphical representation of numerical data. Charts convert data in rows and columns into a picture that can be read at a glance. Charts makedata easier to understand. Trends are revealed, and comparisons can be madeinstantly. Charts can assist people to make quick and accurate decisions.

DatabasesA database is an organised collection of data. A flat file database organises datainto a single table and is suitable for many small applications. Flat file databasesorganise data using data structures called files, records, fields, and characters. Arelational database organises data using a series of related tables. Relationships arebuilt between the tables to provide a flexible way of manipulating and combiningdata. Relational databases are the most popular database structure.

Databases are an important component of most DSSs. They enable users toaccess large amounts of data to make a decision. Retrieving data for decision-making usually requires the construction of a query. A query is a search of adatabase for records that meet a certain condition. It is a question you ask of thedatabase. A query is constructed in the form: <Field name> <Operator> <data>.The data in the query is often called the criteria.A common method for describinga query is query by example (QBE). QBE requires the user to enter the criteriaagainst a field. A query language is a specialised language designed to search thedatabase. There are different query languages, each with its own grammar, syntaxand vocabulary.

A data warehouse is a database that collects information from different datasources. It is a storage area of raw data that can be analysed to assist organisationsto make decisions.A data warehouse involves careful planning to decide what datato collect. The contents of a data warehouse are usually historical and fairly static.A data warehouse is separate from the operational databases and is updated fromthem at specified intervals. An enterprise data warehouse is a centralised store ofdata from many different sources. It sells access to many different users for theirown analysis.

A data mart is a smaller version of a data warehouse. It is a store of data abouta specific topic or area. The emphasis of a data mart is on meeting the specificdemands of a particular group of users in terms of analysis, content, presentation,and ease of use. Data marts may be part of a data warehouse, or they may becreated independently. Data marts allow users to get quick answers to theirqueries.

Expert systemsExpert systems provide information and solve problems that would otherwiserequire a person experienced in that field (an expert). They are designed for usein highly unstructured settings, such as medicine and investment in shares. Expertsystems make a decision based on the knowledge of an expert. However, theirconclusions are not guaranteed. It is up to the user to accept or reject the decision.The main advantage of expert systems is their low cost compared with theexpense of paying an expert or team of specialists.


There are two important components of an expert system: the knowledge baseand the inference engine. The knowledge base is a set of general facts and if-thenrules supplied by an expert. Expert systems generate questions using the know-ledge base and carry out reasoning using the inference engine. For example, amedical expert system might use medical history, the patient’s symptoms andlaboratory test results to help doctors to diagnose infectious blood diseases andprescribe antibiotics.

Neural networksA neural network is an information system that works like the human brain andis capable of learning. It contains a large number of processors connected likenerve cells in the human brain.These processors, or nodes, form a network and actlike cells in the brain.A neural network finds relationships between sets of data todevelop an understanding of the situation. In an early demonstration, researcherstrained a neural network to read aloud. It learned to do this task by being shownthousands of examples. Neural networks are very good at finding a link betweenthe data and a result. They are being used by:• financial firms for economic forecasting and loan approval (see Figure 5.8)• insurers to decide if a potential customer is a good risk• marketers to predict which products will sell• manufacturers to predict how much material they will need• stockmarket firms to make predictions.

157

IITT FFaaccttIT FactThe concept of expert systems originated in the 1960s but first gainedprominence in 1977 when Edward Feigenbaum demonstrated the power ofan expert system to help with decision-making.

Years at address

Input layer Hidden layer Output layer

Years at job

Salary/loan

Health

Approve loan

Disapprove loanCredit rating

Figure 5.8 A simplified neural network to approve or deny a loan.

158 Options

1 List two semi-structured situations where a DSS would be useful.

2 Describe a DSS used by a bank officer to approve a loan.

3 What is an AFIS?

4 What is the role of an expert in an AFIS?

5 List two unstructured situations where a DSS would be useful.

6 How does a DSS predict future stock prices?

7 What is a GIS?

8 List four types of DSS.

9 How does a spreadsheet help with decision-making?

10 Describe the type of data entered into a spreadsheet.

11 Describe the features that make spreadsheets easy to use and suitable for a DSS.

12 Why are databases an important component of most DSSs?

13 Explain the difference between a data warehouse and a data mart.

14 What are expert systems?

15 Describe the main advantage of an expert system.

16 What is a neural network?

17 Where are neural networks being used?

LEARNING ACTIVITIES

1 DSSs perform information processes requiring participants, data/information andinformation technology. Clearly identify the participants, data/information, infor-mation technology and the purpose of the following DSSs:a a bank officer deciding how much to lend a customerb fingerprint matching.

2 Create a spreadsheet using the data in Figure 5.6. Save the spreadsheet with thefilename BOOKS.a Best Books is aiming to make a profit of $1000 for Complete Idiot’s Guide.

What is the minimum number of units needed to be sold to make this profit for this book?

Exercise 5.2

Even though neural networks have been very successful, their applications arestill limited. Most neural networks contain a few thousand nodes compared toabout 100 billion nerve cells in the human brain.As a result, neural networks takea very long time to train, and recognising visual images requires the processing oflarge amounts of data. Neural networks are in the developmental stages, andbillions of dollars are being spent on research. Current applications of neuralnetworks include oil exploration, weather prediction and the exploration ofmodels of thinking and consciousness.

IITT FFaaccttIT FactIn 1982, John Hopfield and several researchers at the California Institute ofTechnology rejected the traditional concept of a computer with a CPU andrunning a program. They built the first machines called ‘neural networks’.


5.3 Organising and decision support systemsOrganising is the modification of data by arranging, representing and formattingdata. It is carried out after the data is collected. In a DSS, it involves designingspreadsheets and constructing the knowledge base of an expert system.

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b Best Books is aiming to make a profit of $2000 for Mastering Spreadsheets.What is the minimum number of units needed to be sold to make this profit forthis book?

c The selling price of each book is calculated by adding 50% to the cost price. BestBooks has decided to have a sale and decrease the markup on all books from50% to 20%. What is the total profit using this markup if the sales figuresremain the same?

d The sale described in question (c) has resulted in an increase in sales of 30% onall books. Add a new column after column B with a heading of ‘New sales’.Enter formulas into this column to calculate the new sales figures. What is thetotal profit based on these sales figures?

e What increase in sales is required to obtain a total profit of $7000? (Make youranswer correct to the nearest whole number.)

3 Create a spreadsheet using the data in Figure 5.7. Save the spreadsheet with thefilename MUSIC.a Mick’s Music needs to determine the total bonus for all of its employees. Enter

a formula in cell F12 to calculate the total bonus.b How much overtime does Sandra White need to complete to receive a total

bonus of $1400?c What is the effect on the total bonus if the additional bonus is increased from

$200 to $250?d What is the effect on the total bonus if the bonus and additional bonus are

calculated on 40 hours of overtime instead of 50 hours?

4 Michael is considering purchasing a restaurant in the local area. Each week therestaurant buys $20 000 of stock for about 250 customers. This stock is sold at aprofit of 60%. The wages bill for the week is $9500, and Michael would need torepay a loan at $5000 per month. Michael needs to analyse this data to determinethe restaurant’s profitability. Construct a spreadsheet to help Michael make hisdecision and save it with the filename MICHAEL. What is the minimum number ofcustomers needed for the restaurant to break even?

5 Melissa works for a tourist bureau. She has been asked to collect and organisedata on popular Australian tourist destinations. The data collected includes thelocation, cost, hours of operation, rating, amenities and characteristics. Develop adatabase solution for Melissa using real or fictitious data and save it with thefilename TOURIST. Melissa needs to use the database to help with decision-making. Describe and demonstrate five different ways the database would helpMelissa make a decision.

6 The Internet contains many Web sites that use and promote a DSS. Describe thefeatures in two Web sites for each the following applications:a predicting stock pricesb home loan analyser.

160 Options

Designing spreadsheetsDesigning spreadsheets involves creating a pen and paper model, identifying datasources, planning the user interface and developing the formulas to be used.

Pen and paperFor centuries, people have used pen and paper to construct rows and columns of

numerical data and manipulate it in some way (see Figure 5.9). For example,people used ledgers to keep records of their sales, incomes and payments.

Today, pen and paper are still used to plan a spreadsheet and create amodel of the situation. How is the spreadsheet going to solve the

problem? What data needs to be entered? How will I obtain thedata? What will the headings and titles be? How will the numbers

look? What is the relationship between the data? Does itrequire a calculation? What formulas are to be used? What

results are required? Creating a spreadsheet may also involve using a

template. A template is a document created forrepeated use. A spreadsheet template contains labelsand formulas to solve a particular problem. The user

enters the values to obtain the required solution.For this reason, a template can save time andeffort.Templates are available in many spreadsheetprograms to help with decision-making.

Data sourcesData is collected for a spreadsheet from a variety of data sources. It may beobtained by researching the topic and selecting relevant facts. The Internet is asource of data.Web sites and newsgroups present information on a range of topics.Data sources may also include interviews, surveys, observations and measure-ments. Data should be gathered in an organised way to ensure nothing is omitted.After the data is collected, it must be carefully interpreted to ensure that theresulting information is valid. For example, can the results of a survey begeneralised to a large group of people? The reliability of the data source is anotherissue. If similar data was gathered at another time and place, would the results bethe same?

User interfaceA spreadsheet must be well-designed and easy to use. There is no correct way todesign a spreadsheet. Each particular problem has its own design requirements.

Figure 5.9 A traditional pen and paper spreadsheet.

IITT FFaaccttIT FactIn a survey of blue-chip companies, more than 90% of large spreadsheetscontained at least one calculation error. Some spreadsheets were so badlywritten they were impossible to test and had to be completely rewritten.


However, a well-designed spreadsheet has four easily identifiable areas: instruc-tion, input, calculation, and output (see Figure 5.10):• Instruction area. The instruction area provides information about the spread-

sheet or directions for use of the spreadsheet. It is usually at the top of thespreadsheet and includes a title, a description, the authors and the creation orrevision date. Larger spreadsheets include a brief outline of their structure,directions and parameters. A parameter is a variable that is given a constantvalue for a particular application.

• Input area. The input area includes labels for headings and the values on whichcalculations are based. The format of the values and labels is often completedafter the data has been entered. For example, when entering money values donot include the dollar sign ($) as these values can be formatted as currency,which will automatically enter the dollar sign. All inputs should be labelledclearly so the user knows where and how to enter the data.

• Calculation area. The calculation area contains the formulas and functions thatcomplete the work of the spreadsheet. The calculation area is the heart of aspreadsheet.

• Output area. The output area displays the result of the spreadsheet. In manyspreadsheets, the output area and the calculation area will be the same. Alloutputs should be clearly labelled so the user understands the results.Presentation of data should be suitable to the type of that data and its use.Often a chart will display the information in a more understandable form fora decision to be made.

161

Figure 5.10 A well-designed spreadsheet.

FormulasA formula is an instruction to perform a calculation. Whenever values arechanged, the formulas are recalculated and produce new results. Formulas consistof four main elements: numbers, cell references, operators and functions:• Cell references allow formulas to refer to other cells in the same sheet or even

cells in other sheets. Cell references are often in the form of a range or name.

Instruction area

Calculation area

Output area

Input area

162 Options

A name is assigned to a cell reference or to a range to make the spreadsheeteasier to use. For example, in the formula =SUM(FirstQuarterSales), thename FirstQuarterSales represents the range C20:C30 on the sheet namedSales. It is easier to identify than =SUM(Sales!C20:C30).

• Operators are used to perform a process and are used to construct the requiredformulas. Operators can be grouped as arithmetic, relational or text (see Table 5.2).

Operator Description ExampleArithmetic

+ addition =6+2 gives 8

– subtraction =6–2 gives 4

* multiplication =6*2 gives 12

/ division =6/2 gives 3

^ exponentiation =6^2 gives 36

% per cent =15% gives 0.15

Relational

= equal to =3+2=4 gives FALSE

<> not equal to =22–1<>20 gives TRUE

< less than =22<20 gives FALSE

> greater than =22>20 gives TRUE

<= less than or equal to =15+4<=20 gives TRUE

>= greater than or equal to =15+4>=20 gives FALSE

Text

& text joining =’A=’&FALSE gives A=FALSE

Table 5.2 Some spreadsheet operators.

• Functions perform a simple or complex calculation. Special rules or syntaxmust be followed when functions are used. Functions consist of a functionname, such as SUM; one or more sets of parentheses (()); and arguments (seeTable 5.3). Arguments are the values on which the functions operate, such asthe range of cells B4:B8 in the formula =SUM(B4:B8).Cell references make a spreadsheet very flexible. The value in a cell can be

changed and the results seen without having to change the formulas. This processcan be repeated many times, and it assists in decision-making. If a formula refersto itself, either directly or indirectly, it is called a circular reference. For example,if the contents of cell B4 were =B4+1, this would be a circular reference. It willresult in an endless loop, and an error message will be displayed. When a formulais copied, the content of the formula in its new location may change or it mayremain exactly the same, depending on whether absolute referencing and relativereferencing was used to construct the formula:• With absolute referencing (also called absolute addressing), the formula is

copied exactly, with the cell references remaining the same. Using the dollarsign ($) in the cell reference (for example, $A$1) indicates that it is an absolutecell reference. For example, if the formula =$B$5*$C$5 in cell D5 is copied to

Decision support systems 163

Function Description ExampleArithmetic

ABS absolute value =ABS(–12) gives 12

INT integer part =INT(2.99) gives 2

LOOKUP searches a range of cells for =LOOKUP(B6,A9:C14)for a lookup value

PI mathematical constant =PI()

ROUND rounds to a number of =ROUND(3.14159,3) gives 3.142decimal places

SQRT square root of a value =SQRT(144) gives 12

SUM adds up all the values in a list =SUM(B4,B5,B6,B7)

Statistical

AVERAGE average of its arguments =AVERAGE(2,4) gives 3

COUNT how many numbers in the =COUNT(5,1,12,5) gives 4list of arguments

MAX maximum value in a list of =MAX(3,6,1,4) gives 6arguments

MEDIAN median (middle) of the given =MEDIAN(8,3,10) gives 8numbers

MODE most common value =MODE(4,6,6,4,4,4) gives 4

MIN minimum value in a list of =MIN(3,6,1,4) gives 1arguments

STDEV standard deviation =STDEV(5,10,15) gives 5

Logical

AND returns TRUE if all the =AND(2+2=4,2+3=5)arguments are true; gives TRUEreturns FALSE if one or more =AND(2+2=5,2+3=5)arguments are FALSE gives FALSE

FALSE returns the logical value FALSE =FALSE()

IF returns one value if logical =IF(5<7,1,2) gives 1test evaluates to TRUE and =IF(8<7,1,2) gives 2another value if it evaluatesto FALSE

NOT reverses the logic of the =NOT(1+1=2) gives FALSEargument

OR returns TRUE if any argument =OR(1+1=2,2+2=5) gives TRUEis TRUE; returns FALSE if all =OR(1+1=1,2+2=5) gives FALSEarguments are FALSE

TRUE returns the logical value TRUE =TRUE()

Table 5.3 Some spreadsheet functions.

cell D6, the new formula is identical (=$B$5*$C$5) and the result of theformula stays the same.

• With relative referencing (also called relative addressing), the mathematicalprocesses, such as the operators and functions, are copied but the cellreferences change so that they relate to the destination. For example, if theformula =B5*C5 in cell D5 is copied to cell D6, the new formula wouldbecome =B6*C6. The cell references have changed relative to the destination.

164 Options

It is possible to have a formula containing both absolute and relative refer-ences. This is called a mixed cell reference. For example, if the formula=LOOKUP(A5,$B$15:$C$22) in cell C5 is copied to cell C6, the new formulawould become =LOOKUP(A6,$B$15:$C$22) (see Figure 5.11).

Constructing a knowledge baseA knowledge base is a set of general facts and if-then rules supplied by an expert.If the condition is true, then a certain deduction is made. For example, IF it has 4 legs, THEN it is a dog. This deduction would not always be valid. A moreaccurate deduction is obtained by using a set of if-then rules. For example, IF ithas 4 legs AND IF it has a tail AND IF it barks,THEN it is a dog (see Figure 5.12).

Each if-then rule is combined using the AND operator or the OR operator.When the AND operator is used, each condition must be true for the deductionto be made. When the OR operator is used, only one of the conditions must be true for the deduction to be made. For example, a knowledge base to screenjob seekers:

IF: applicant_occupation NOT = "retired" AND

IF: hours_worked > 12

THEN: applicant_status = "worker".

A knowledge base is often constructed using expert system shells (also calledshells). Expert system shells are a ready-made expert system except that theycontain no knowledge. When the knowledge is entered, it results in an expert

Figure 5.11 Spreadsheet showing a mixed cell reference.

= LOOKUP(A5,$B$15:$B$22,$D$15:$D$22)

= B5*C5

= LOOKUP(A5,$B$15:$C$22)


system. Shells provide an interface to assist the user in creating an expert system.The shell queries the user for facts and for links between the facts. It enters thisdata into the knowledge base.The majority of shells represent knowledge using if-then rules. The shell displays the word IF on the screen, and the user enters theconditions.The deductions (THENs) are added after the conditions (IFs).When aset of if-then rules is completed, the shell builds a knowledge base and an infer-ence engine. Expert system shells allow expert systems to be built very quickly.The great majority of expert systems in Australia have been built using shells.

MYCIN is a famous expert system developed in the 1970s at StanfordUniversity in California. It was designed to assist non-specialist doctors in thediagnosis and treatment of bacterial blood infections. MYCIN asks the doctorabout cultures grown from samples taken from the site of infection and the resultsof other tests. The knowledge base about bacterial infections is coded in if-thenrules similar to following:

IF: The stain of the organism is Gram-negative AND

IF: The morphology of the organism is rod AND

IF: The aerobicity of the organism is aerobic

THEN: The suggestive evidence is that the organismis Enterobacteriaceae.

165

Antecedent

IFIt has four legs

AND IFIt has a tail

AND IFIt has fur

It is a dog

AND IFIt barks

AND IFIt meows It is a cat

Conclusion

Figure 5.12 With if-then rules, different combinations lead to differentdeductions.

1 List the questions answered using pen and paper to design a spreadsheet.

2 What is a template?

3 Describe some of the data sources for a DSS.

4 Describe the four main areas used in the layout of a spreadsheet.

5 List four main elements in a formula.

6 What is a ‘name’ in a spreadsheet?

7 What is a circular reference?

Exercise 5.3

166 Options

8 Explain the difference between an absolute and a relative reference.

9 What is a mixed cell reference?

10 What are if-then rules in a knowledge base?

11 Explain the difference between the AND and OR operator as they are applied in aknowledge base.

12 Design a set of if-then rules to identify a cat.

13 What is an expert system shell?

14 What is the purpose of MYCIN?

15 What are the results of the following formulas:a =8+2*5+7b =9^2 + (24/6)c =AVERAGE(8,12)d =COUNT(6,2,14,7)e =SUM(1,5,9,12)f =MAX(8,5,1,9,8)g =IF(6<12,5,10)h =IF(13<12,5,10)

LEARNING ACTIVITIES

1 Create a spreadsheet using the data in Figure 5.11. Save the spreadsheet with thefilename ACE.a Enter each employee ID from the lookup table into cells A6 to A12.b Enter dummy data into cells B6 to B12 to represent the hours worked for each

employee.c Copy the formulas in cells C5:E5 to cells C12:E12. Examine the formulas in cells

C6, D6 and E6. What changes have occurred?d Todd Bradley is hired by Ace Technology. His employee ID is 945, hourly rate $14

and bank account number 7881225. Enter this data into row 23. Modify thespreadsheet so that it will calculate Todd’s weekly wage.

e Ace Technology needs to determine the total weekly wage for all of itsemployees and the average hourly pay rate per employee. Edit the spreadsheetto do these calculations.

f What would the total weekly wage bill be if every employee worked 35 hoursa week?

g What would the total weekly wage bill be if every employee received an hourlypay rate of $20?

2 Create a spreadsheet template that could be used as a personal budget for a Year12 student. Save the spreadsheet as a template with the filename BUDTEMP. Thetemplate is to contain possible sources of income and expenses. Formulas are to beused to calculate total income and expenses and to balance the budget. Enter arange of values. List five what-if questions that could be asked of the spreadsheetfor decision-making.

3 A video shop is having problems meeting its costs. It needs to decide whether itshould increase its rental prices. Design a spreadsheet model that could be usedto estimate the effects of different rental prices on revenue and the number ofrentals. Visit a local video store to obtain current price structures and typicalweekly rental numbers. Construct a well-designed spreadsheet. What will theeffect of increasing rental prices be?


4 A person is eligible to drive if he or she is 16 years and 9 months old and haspassed a practical test and a theoretical test. Write down the if-then rules thatcould be used in an expert system to determine whether a person is eligible todrive.

5 An expert system is to be designed to assist a pet-shop owner to suggest a suitablepet for a customer. Create a knowledge base of if-then rules that could be used inthe expert system. Design some test data to verify the rules.

6 Use an expert system shell to create a simple expert system. Choose a situation inwhich you are the expert. Simple expert system shells can be downloaded fromthe Internet.

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5.4 Processing and decision support systemsProcessing in DSSs is the manipulation of data by editing it and updating it. Thissection describes the structure of expert systems, how they deal with data and theinclusion of certainty factors to handle unclear situations. It also includes a sectionon macros as valuable tools in the processing of spreadsheet models.

The structure of expert systemsAn expert system has four major components: a knowledge base, a database offacts, an inference engine and an explanation mechanism.

Knowledge baseThe knowledge base is a set of general facts and if-then rules supplied by anexpert. It is the heart of an expert system as it contains the detailed knowledgesupplied by an expert. The knowledge base is in the form of rules, such as if-thenrules. A knowledge base can contain just a few rules or thousands depending onthe scope of the expert system.The knowledge of an expert is expressed using theif-then rules in the knowledge base.

Database of factsThe database of facts is the data that relates to the specific situation beinganalysed. The database of facts is used by the inference engine when it is workingon a problem. It is simply a table. The database of facts holds the data about thecurrent task, such as the user’s answers to questions, data from outside sources,intermediate results of the reasoning or conclusions reached so far.There is a cleardistinction between the knowledge base and the database of facts.The database offacts contains data about the current problem. For example, a knowledge base topredict sales would contain data from a range of different companies. However,the database of facts would contain data from a specific company and its tradingperformance.

Inference engineThe inference engine is the part of the expert system that carries out thereasoning. It is a set of routines that carries out deductive reasoning by applying the facts, assumptions, theories, and rules in the knowledge base. It carries out the

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reasoning by following a set of strict logical processes as opposed to the richnessof human reasoning. The inference engine applies the if-then rules in the know-ledge base plus the database of facts to decide what question to ask next. It isessentially a rule interpreter whose function is to use the if-then rules, facts andother items in the knowledge base to solve the problem set by the user.

Explanation mechanismThe explanation mechanism is a method of checking how the expert systeminferred its deduction. Experts systems do not guarantee decisions; it is always upto the user to make a final judgement. If users check the explanation mechanism,they find out how a particular fact was inferred or why a particular question isbeing asked. The explanation mechanism confirms the series of inferences thathave led to a conclusion or to a particular question being asked.

Types of inference engineThere are two main types of inference engines: forward chaining and backwardchaining.

Forward chainingForward chaining is an inference strategy in which the user supplies all the databefore the question is asked or the inference is made. It begins with data andworks forward to see if any conclusions can be reached. Forward chaining is oftenused when there is no clear goal and the system is just attempting to determine allof the conclusions implied by the data. For example, in forward chaining youmight be asked a series of questions about your eating habits. Forward chainingthen draws an inference or conclusion based on your answers, such as you have ahealthy diet.

Backward chainingBackward chaining starts with one or more possible solutions and searches backthrough the system to determine the questions to be asked. It is also known as‘goal-directed reasoning’ or ‘conclusion-driven reasoning’. Backward chainingstarts with a tentative conclusion and searches back through the rules for thequestions or facts that support that conclusion. Backward chaining works in theopposite direction to forward chaining. It starts with the tentative conclusion, suchas you are on a healthy diet, and then asks all the questions to ensure the usermeets the conditions (see Table 5.4).

Backward chaining Forward chainingStarts from Possible solutions New data

Works towards New data Any conclusions

Progression through rules Conclusions to conditions Conditions to conclusion

Style Conservative Opportunisitic

Processing Efficient Possibly wasteful

User’s impression Plodding but predictable Responsive but quirky

Obvious usage Selection between Building up solutions andalternative solutions ‘leaps’ in reasoning

Table 5.4 Comparison of backward and forward chaining.


Backward and forward chaining have different uses and different effects.Although they proceed in opposite directions, an expert system might use themin combination.A doctor’s typical analysis process is a combination of forward andbackward chaining. The doctor starts with a brief medical history and draws sometentative conclusions (forward chaining).The doctor then uses backward chainingto confirm or deny the diagnosis (see Figure 5.13).

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Forward Chaining

Bump on head

Vomited

Disorientated

Head Injury

Nausea Suspect brainhaemorrhage

Eliminate brainhaemorrhage

Dizziness

Perform CAT scan

Backward Chaining

Figure 5.13 Forward chaining versus backward chaining.

Fuzzy logicFuzzy logic describes the variables that exist between a ‘true’ and a ‘false’. Forexample, a piece of information might be ‘fairly’ true. Fuzzy logic seems closer tothe way our brains work.We combine data and form a number of partial truths onmany topics. Fuzzy logic is used in neural networks and expert systems.

The results of fuzzy logic operations may be expressed as probabilities orpossibilities. Fuzzy logic relies on historical data, mathematical probabilities andrules. Consider this unclear situation: ‘If Stella is tired, then there’s quite a goodchance she’ll be in a bad mood’.The expert system must interpret the meaning ofthe words ‘a good chance’. It does this by adding certainty values, or probabilities,to the rule and attaching certainties to any new conclusions. Thus, fuzzy logicmight conclude that Stella is probably in a bad mood and that this conclusion hasa certainty value of 0.6.

Fuzzy logic is based on probability theory. However, it is much less rigorousthan probability theory and aims for a good guess rather than a precise probability.The basic idea is to add certainty factors to rules and use these to calculate themeasure of belief in some deduction. Certainty factors are often based on therough guesses, or rules of thumb, of experts rather than on actual statisticalknowledge. They are easily updated if new information is received. The followingif-then rules have certainty values attached:

IF: car won’t start

THEN: battery is flat (certainty value = 0.7)

IF: car won’t start

THEN: starter motor is broken (certainty value = 0.2).

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The certainty values in the example are based on the expert’s knowledge orguess about how often flat batteries are the cause of a car not starting versus howoften broken starter motors are the cause.

MacrosA macro is a series of commands stored in a file that can be executed by pressinga few keys. Macros allow many operations to be performed automatically, such asopening menus, choosing commands or entering text. Macros save time andreduce keyboard errors. Any sequence of actions that a user performs can berecorded as a macro. For example, your name may appear in all your spreadsheets.If you store your name in a macro assigned to the ‘F2’ key, then every time youpress the ‘F2’ key, the macro will type your name.

To record a macro, select the ‘Record New Macro’ command. The commandwill ask for a name for the macro so it can be saved as a file and will ask which keyor keys to assign the macro to. After you enter a name and key assignment, themacro recorder starts working. Each action that you complete will beremembered. Do the task that the macro will perform. When all the actions arecompleted, turn off the macro recorder by selecting the ‘Stop Recorder’command. The macro is used by selecting the ‘Run Macro’ command. Thiscommand will carry out all the actions stored in the macro. Macros are used to automatically move to specific areas of the spreadsheet, to sort data areas or toformat areas. Macros can also be created using programming languages, such asVisual Basic.

1 List the four major components of an expert system.

2 Explain the difference between a knowledge base and a database of facts.

3 What is an inference engine?

4 How is the explanation mechanism used in decision-making?

5 What is forward chaining?

6 Describe a situation that combines forward and backward chaining.

7 What is fuzzy logic?

8 What is a certainty value?

9 How is fuzzy logic calculated?

10 What is the meaning of a conclusion with a certainty factor of 0.2?

11 How do you record a macro?

LEARNING ACTIVITIES

1 A person’s results from a series of tests, such as running up stairs or throwing aball, are entered into a sports expert system. The expert system then suggests themost appropriate sport for that person.a Describe the type of information held by the knowledge base. Your answer

should include some if-then rules.b Describe the type of information held by the database of facts.c Do you think the expert system is using forward chaining or backward chaining?

Justify your answer.

Exercise 5.4


5.5 Analysing and decision support systemsAnalysing in a DSS is the interpretation of the data. It involves examining the dataand giving meaning to it. This section looks at methods of extracting relevantinformation from spreadsheets and databases. It also compares and contrasts thedifferent methods of matching data used by databases, neural networks and expertsystems.

Data miningData mining is a process that finds relationships and patterns in the data stored ina database. It sorts through the data and turns up interesting and often usefulconnections. Intelligent agents are pieces of software used in data mining to searchthrough relational databases for relevant data. For example, data mining could beused to analyse the transactions at the supermarket. It might determine that therewas a relationship between tomato sauce sales and meat pie sales.This informationmight be useful for marketing promotions. The main purpose of data mining is toidentify new marketing opportunities and to target particular niche markets.However, one problem with data mining is that many of the patterns occur bychance and have no value in making decisions. Data mining also raises issues ofprivacy and ownership of data.

Data mining identifies patterns in data and infers rules from these patterns. Itthen uses additional data to refine the rules based on the original patterns of data.Results from data mining include:

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2 Sarah is prepared to invest somewhere between $3000 to $15 000 in a financialinstitution. Investigate the current interest rates for a term deposit at threedifferent financial institutions. Sarah needs to make a decision on the amount ofthe investment and the length of her investment. a Construct a spreadsheet with clearly defined instruction, input, calculation and

output areas. Save the spreadsheet with the filename SARAH.b Create a simple macro to automatically move to each specific area of the

spreadsheet.c What is the effect of different interest rates on her investment? If you had this

amount of money, where would you invest it? Estimate the return for yourinvestment and include it on the spreadsheet.

3 How can backward chaining be used to draw conclusions in an expert systembased on the following set of rules:

If wage > $50 000, then wage is good.

If assets > $120 000, then credit risk is good.

If wage is good and credit risk is good, then grant loan.

4 An expert system uses the following if-then rules: IF has-spots(X) AND has-fever(X),THEN has-measles(X). Certainty factor is 0.5. What is the meaning of the fuzzylogic in this situation?

5 Name three situations where fuzzy logic needs to be applied. Describe thesesituations using if-then rules and attach certainty factors to the conclusions.

6 ‘Intelligent enterprise’ is a rapidly growing aspect of the Internet. Search the Webto obtain information on this topic. (Try www.intelligententerprise.com.)

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• linking a number of events together, such as linking two mandatory courses sothey are timetabled at different times

• identifying patterns, such as a sequence of courses over a number of years thatstudents commonly choose

• organising data into patterns, such as the length of degree• inferring rules from certain subgroups that distinguish them from other groups,

such as groups based on age or interest.Internet search engines, such as AltaVista, provide data mining tools to assist

with finding information on the Internet. These sites maintain large databases ofinformation about Web pages.Their search engines have Web crawlers that searchthe Web and group sites into classifications. Users can search for relevant Web sitesby using the classifications and subject headings.

IITT FFaaccttIT FactSearch engines are a relatively ancient technology. In the 1970s, a searchengine was used by IBM to search voluminous text files created by lawyersdefending IBM against a U.S. Government anti-trust suit.

Extracting summary dataThe purpose of a spreadsheet is to produce information in a useful form to assistdecision-making. It changes data into information by performing calculations.However, information is difficult to understand when too much information ispresented or it is in the wrong format. Extracting summary data from aspreadsheet may involve using a range of different tools:• Filtering data so that it will display only the desired data. For example, a

spreadsheet of international sales data can be filtered to only show theAustralian sales data. Extracting summary data is often easier if the data issorted.

• A report allows you to insert headings and titles and choose the information tobe printed. Spreadsheet programs allow the user to prepare more than onereport from the same spreadsheet.

• A pivot table is an interactive table that quickly summarises large amounts ofdata. The user specifies the data and the calculations to be performed. Whenthe table is built, it is possible to rotate the rows and columns to see differentsummaries. This ability to pivot the dimensions of the table makes it a verypowerful tool. Pivot tables are linked to the original data in the spreadsheet.

Spreadsheet analysisSpreadsheets are analysed in many different ways to obtained information andhelp with decision-making. Three of these methods are what-if models, statisticalanalysis and charts.

What-if models A what-if model, or sensitivity analysis, is the process of making changes to thedata and observing their effects. For example, in a budget spreadsheet, the usercould change one of the expenses and observe the effect on the balance (see


Figure 5.14). Most spreadsheet programs allow data from other sources to be used. Data can be imported from relational databases or even from the Internet.This allows different sets of data, or scenarios, to be used within the samespreadsheet model. For example, in the budget spreadsheet the user could use anew sheet for each family member. Each sheet would have a set of values for thatperson. The ‘what-if’ analysis is then performed using a combination of the datain each sheet.

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Figure 5.14 Spreadsheet used for what-if questions.

Statistical analysisSpreadsheet programs contain many built-in statistical functions. Statisticalfunctions are used to analyse and interpret data. Table 5.3 on page 163 describesseven statistical functions commonly used in a spreadsheet for statistical analysis,such as STDEV. Statistical functions are often used to construct statistical modelsthat perform complicated analyses, such as analysis of variance or regressionanalysis. A linear regression model is the best-fit relationship between two typesof data, such as sales and money spent on marketing (see Figure 5.15). Anorganisation might develop a linear regression model to estimate future salesbased on past experience.

ChartsA chart is a graphical representation of numerical data. Charts convert data inrows and columns into pictures that can be read at a glance (see Figure 5.16). Textand tables require close study to obtain a general impression of a subject. Chartsmake data easier to understand: trends are revealed and comparisons are madeinstantly. Charts can help people make quick and accurate decisions. There aremany different types of charts, including bar, column, line and pie charts:

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• A bar chart allows comparisons between items to be made at a glance andshows variation over a period of time. A bar chart presents data in horizontalrectangles.The length of the rectangle gives a visual representation of its value.In bar charts, numeric values are plotted along the X-axis, and categories areplotted along the Y-axis.

• A column chart also allows comparisons between items to be made at a glanceand shows variation over a period of time. A column chart presents data invertical rectangles, and the length of each rectangle gives a visual repre-sentation of its value. In column charts, categories are plotted along the X-axis,and numeric values are plotted along the Y-axis.

• A line chart shows trends or changes in data over a period of time. It emphasisestime flow and rate of change rather than the amount of change. A line chartpresents data by joining a line between adjacent values. Each value is plotted asa dot called a data marker or datapoint. In line charts, categories areusually plotted along the X-axis,and numeric values are plottedalong the Y-axis.

• A pie chart shows the relationship,or proportions, of parts to a whole.Pie charts appeal to peoplebecause they are easy to read andattractive.A pie chart presents dataas sectors of a circle. Sectors of acircle are similar to slices of a pie.

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01.1 1.3 1.2 1.5 1.4 1.4 2.5 2.8 2.8 2.8

Advertising ($ million/month)

Sale

s ($

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th)

Advertising($M/month)

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Trend line

Figure 5.15 A linear regression model for predicting sales volume.

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01 2

Warehouses

Warehouses against location

Distance

Hour & costCos

t

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Figure 5.16 Charts convert data into picturesthat can be read at a glance.


Data matchingData matching involves finding data and giving some meaning to it. DSSs usedifferent ways to match data in a database, a neural network and an expert system.Data matching in:• a database involves searching and sorting data. It requires the user to construct

an appropriate query and interpret the results. Data matching in a datawarehouse is achieved using data mining. It finds relationships and patterns inthe data stored in a database.

• a neural network is achieved by finding relationships between sets of data todevelop an understanding of the situation. Neural networks are capable of learn-ing. They examine the data and create new information as they are training.

• an expert system involves the use of a knowledge base, a database of facts andan inference engine. The knowledge base and database of facts contain all the data, and the inference engine carries out the reasoning by using the facts,assumptions, theories, and rules.Both the database and the expert system have a fixed body of data, unlike the

neural network whose learning may create more data and information. However,this distinction is blurring. For example, many recent expert systems have a neuralnetwork component to allow them to learn. In addition, data mining used in datawarehouses applies many of the techniques from neural networks to discover newinformation.

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1 What is the purpose of data mining?

2 Describe four results obtained from data mining.

3 List three tools for extracting summary data from a spreadsheet.

4 Why is data filtered?

5 What is a pivot table?

6 List three ways that spreadsheets can be analysed.

7 What is a linear regression model?

8 Describe the four different types of charts that are commonly used to displayinformation.

9 What is data matching?

10 How is data matching achieved in a neural network?

11 Explain a distinction in data matching between the database and expert systemcompared to a neural network.

LEARNING ACTIVITIES

1 Create separate spreadsheets and an appropriate chart for the following data:a Compare sales figures over two days at the following stores to show any

variation over time: Castle Hill, $15 000 and $13 000; Rose Bay, $17 000 and$18 000; Parramatta, $23 000 and $26 000; and Campbelltown, $12 000 and$10 000.

b Show the proportions of parts to the whole for the following age groups: 0 to20, 36%; 20 to 40, 26%; 40 to 60, 24%; and 60 to 80, 14%.

c Analyse each of the above spreadsheets and draw a conclusion based on youranalysis.

Exercise 5.5

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5.6 Other information processesAll information processes play a role in decision support systems, includingcollecting and storing and retrieving.

CollectingCollecting is the information process that involves deciding what to collect,locating it and collecting it. In DSSs, it involves identifying data and identifyingthe roles of the expert and the knowledge engineer in the creation of expertsystems.

Identification of dataWhen collecting data for DSSs, it is important to know what decisions you haveto make. This determines whether the source of data is primary or secondary.Primary source is when data is collected first hand. Many organisations generatetheir own primary source data because they consider it more meaningful andreliable, although it is time consuming and costly. Data from primary sources isacquired through interviewing people, conducting surveys and questionnaires, orobserving the system in operation. Secondary source is when data is collected orcreated by someone else, such as data collected from newspapers, books, otherprint media, electronic databases, CD-ROMs and the Internet. This is often thequickest and least costly method of collecting data, but it may be less meaningfuland reliable than primary source data.

After the data is gathered, it is often classified as structured or unstructured.Structured data is predefined characters, usually numbers, whose meaning andformat is specified. It is easily stored and retrieved in an orderly manner fordecision-making. Spreadsheets and many databases use structured data. Unstruc-tured data does not fit a predefined or descriptive model. It includes all types ofmedia, such as text, audio, numbers, images and video. Unstructured data is moredifficult to use in DSSs as it creates greater processing and storage demands.

When collecting data for DSSs, users should consider the data range, time spanand level of detail. The data range is the amount of data and the number ofsources.To make a strategic decision, management may need a wide range of data,

2 Michelle has accepted a position as a librarian. She is moving away from home andconcerned about her finances. Develop a spreadsheet to analyse Michelle’sfinances. Michelle will receive $40 126 per annum (before tax) as a librarian and ispaid fortnightly. She has $4500 invested in a bank, and interest is paid half-yearly.Michelle wants to purchase a car and needs a personal loan of $30 000 from abank. Payments will be paid monthly for five years. Michelle needs to budget forthe following expenses: rent, food, utilities, clothing, entertainment, carrepayments and savings. She is hoping to save some money for a holiday at theend of the year. Investigate your local community to obtain appropriate livingexpenses, then:a Design a spreadsheet for Michelle’s finances. Save the spreadsheet with the

filename MICHELLE.b Use some of the statistical functions to analyse the spreadsheet.c Construct appropriate charts to help analyse the spreadsheet.d Create some what-if models and draw a conclusion based on your analysis.


such as the average monthly amount spent on advertising over the last ten yearsby companies in the same industry.Although the required information is only onenumber, it is derived from vast amounts of data from many organisations over along time period. This data would have a broad data range, a wide time span (tenyears) and a low level of detail (one number).

The role of the expertExpert systems collect data from a person experienced in that field, or an expert.The expert supplies the knowledge for the knowledge base and the inferenceengine. The quality of an expert system is dependent on the knowledge of theexpert. Expertise is the skill and knowledge, generally gained by experience, that,when applied to a problem, results in a performance well above the normal.Expertise often consists of large amounts of factual information that is appliedusing specific rules to analyse a problem in an efficient manner. Most rules thatexperts use are heuristic. Heuristic rules require more than ordinary knowledge;they are put together from the experts’ experience and hindsight.

The role of the knowledge engineerKnowledge engineers are the people who build the expert system (see Figure5.17).They are responsible for obtaining information from the human experts andfor designing the structure of the knowledge base and the inference engine. Aknowledge engineer will help experts describe their knowledge and design anexpert system that is attractive and useful. The information presented by theexpert system should be displayed using language that is appropriate to theintended user of the expert system.

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Figure 5.17 A knowledge engineer.

Knowledge engineering is an interactive procedure performed by the knowledgeengineer and the expert to develop an expert system that will solve a problem.Knowledge engineers need not be experts themselves and should not think thatthey are experts. However, a broad experience in the field is a distinct advantagewhen the knowledge engineer has to solve a new problem. Knowledge engineerstend to be verbal, curious and quick to understand complex relationships.

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Storing and retrievingStoring and retrieving data is a two-step process for retaining data. In DSSs, datais stored in large databases, such as data warehouses, with intelligent agents usedto search and retrieve data.

Businesses have always relied on unstructured information. The amount ofunstructured information, such as the Internet with Web sites, email and news-groups, is increasing at a staggering rate. The rapid increase in information hasreached the point where people are being frustrated by information overload.Decision-makers are facing an increasingly challenging task in searching throughthe available sources of information to find the most appropriate ones. Intelligentagents are tools to help decision-makers.

Intelligent agentsIntelligent agents are pieces of software that search through relational databasesfor relevant data. They use neural networks to efficiently search vast amounts ofdata. Intelligent agents are independent goal-directed agents that can be launchedinto a computer system or network to operate in the background. Intelligentagents are used in data mining to find relationships and patterns in the data storedin a database. However, the most common use of these agents is on the Internet,such as an email agent or a news agent. An email agent can screen a user’sincoming email for those requiring immediate action. Similarly, a news agent canbe trained to scan articles in a news service and to deliver a personal bulletin basedon the user’s preferences. The main purpose of intelligent agents is to carry outthese tasks faster and more effectively than a human. The hardest thing toprogram into these agents is commonsense.

IITT FFaaccttIT FactAn intelligent agent is sometimes called a bot (short for robot). They have been developed to personalise information on a Web site based onregistration information and usage analysis.

1 Explain the difference between primary source and secondary source.2 Describe structured data.3 What is the meaning of data range?4 Describe the role of the expert in an expert system.5 What are heuristic rules?6 Describe the role of the knowledge engineer.7 What is an intelligent agent?8 Describe how an intelligent agent works.9 List two examples of the use of an intelligent agent.

10 Outline the main purpose of an intelligent agent.

LEARNING ACTIVITIES1 The source of data for a particular DSS depends on the particular problem:

a A punter intends to train a neural network program to select winners of horseraces. Suggest sources and types of data that could be included in a trainingdatabase.

Exercise 5.6


5.7 Issues related to decisionsupport systemsBoth positive and negative impacts arise in the use of a DSS. In this section, weexamine some of the issues raised by the increasing use of DSS by decisionmakers.

Intelligent systemsScientists are aiming to give computers the ability to think like humans; this is called artificial intelligence, or AI. Artificial intelligence is behaviour by acomputer system that, if exhibited by people, would be called intelligent.Artificialintelligence is used by intelligent systems. Intelligent systems receive data fromthe environment, react to that data and produce an intelligent response (see Figure5.18). They are used in DSSs, such as expert systems, to perform the followingfunctions.

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b A knowledge engineer is constructing an expert system to assess eligibility forbank loans. Suggest sources of data for the knowledge base.

c A manager is constructing a spreadsheet model to assist with long-rangeplanning. Describe some of the primary and secondary sources of data thatmight be relevant.

2 There are many popular search engines. Review at least four search engine sites,including an Australian site, such as webwombat; a meta search engine, such asdogpile; and a special-interest search engine.a How are they different? Do they have different rules for using keywords?b Pick a topic that interests you. Using the same keywords, try your search in the

four search engines. Did you get different results? c Write a short review of the results of your research.

Figure 5.18 The Sendai railway system in Japan operates without drivers, usingartificial intelligence.

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Preserving expert’s knowledgePreserving an expert’s knowledge is one of the reasons for developing an expertsystem. The factual knowledge supplied by an expert is maintained and appliedeven after the expert has changed jobs or moved locations. For example, theknowledge of specialist doctors can be used to create an expert system. This allowsother doctors without specialist training to access the knowledge of the specialistdoctors. An expert system can also combine the knowledge of many differentexperts. Once the expert system has been created, the expert’s knowledge isstored and available to a range of different users.

It can also be argued that a DSS has resulted in a loss of expert knowledge.That is, the use of a DSS has resulted in jobs that now require less expertise, suchas tasks involved in authorising, scheduling, pricing and buying. For example, loanofficers have become dependent on the use of a DSS for the approval of a loan.They do not require the same level of expertise as a loan officer without a DSS.

Improving performance and consistencyDSSs have improved performance and consistency in decision-making. This wasthe original reason for creating a DSS. In general, people make decisions in alimited amount of time based on limited information and with limited processing.A common problem with decision-making is that the language used to describethe information influences decision-makers. For example, an 80% chance ofsuccess seems much more positive than a 20% chance of failure. People often giveundue weight to the most recent information, are too confident, or are not pre-pared to change their opinion. Think about the last decision that you made. Didyou collect all the relevant information and consider all the possible alternatives?

Expert systems will arrive at a decision based on the knowledge of the expert.These decisions are not objective but are based on the relevant facts of the prob-lem. The decision-making is consistent but not always correct. An expert systemonly assists decision-making; it is up to the user to make the final judgement.

Making rapid decisionsDSSs make rapid decisions. They are substantially quicker and more consistentthan an expert in many situations where large amounts of data and numerousalternatives are to be considered. A DSS provides more information and helps togenerate and define alternatives.

Analysing unstructured situationsDSSs using neural networks and expert systems have improved decision-makingin unstructured areas, such as disaster relief management, mining exploration andpredicting share prices. In an unstructured situation, there is no single method toreach a decision and no guarantee that the decision will be correct. There are toomany factors or too little knowledge about the situation. DSSs are used to analyseunstructured situations and provide information to make the situation semi-structured. They reduce the problem to obtain a manageable number ofalternative solutions, but they don’t always result in the best solution.

Data miningData mining is the process of finding relationships and patterns in the data storedin a database. It sorts through the data and turns up interesting and often useful


connections. The information obtained from data mining allows organisations tomake more informed decisions in such areas as improving marketing campaigns or siting a new store. However, it does raise the issues of erroneous inferences and privacy.

Erroneous inferencesData mining identifies patterns in data and infers rules from these patterns. It thenuses additional data to refine the rules based on the original patterns of data.Erroneous inferences occur when these rules are incorrect. This happens becausemany patterns occur by chance, and there is no relationship between the data. Forexample, the fact that the sales of ice cream in Sydney are linked to the sales of socks in Melbourne is a low probability relationship. People need to applycommonsense when analysing the results from data mining. Decisions made fromdata mining must be checked to avoid using an erroneous inference.

PrivacyPrivacy is the ability of an individual to control personal data. Personal data usedin data mining is often used in an unintentional way. For example, some businessescollect and sell information about their customers’ buying habits. Information iscollected at the checkout and combined with a customer profile. The customerprofile is obtained by enticing a customer to use a special card for a discount, suchas earning Frequent Flyer points. This card provides the business with details ofage, sex, income, job and address. Data mining finds relationships between thecustomers’ buying habits and their customer profiles. This information is veryvaluable for marketing products and providing better services to customers.However, people’s personal data is being used without their permission. People’sprivacy is being invaded.

The issue of privacy has always existed. However, information technology iswidening the scope of the issue and making the invasion of privacy much easier.Many common activities leave an electronic trail. Every time a person uses a creditcard or surfs the net, data is added to a database. Data mining is being used toanalyse this data and find relationships. The Internet has countless Web sites thatrequest information from users.Whenever users fill out a form, they are providingvaluable information. Privacy is invaded when an email from an unknownorganisation is sent to an email address and it uses the receiver’s name.This makessome people very angry.

The information technology industry is currently self-regulated. There aremany Web sites that provide disclaimers stating that any information provided willnot be used for other purposes. However, these organisations may not have controlof the data in their databases. The federal government has realised that self-regulation is inadequate and is preparing further legislation for privacy protection.

Group decision support systemsMany decisions are made by people in groups. A group decision support system(GDSS) is an information system that assists users to make a decision by workingtogether in a group. GDSSs have the potential to improve both the efficiency and the effectiveness of some kinds of decision-making. A GDSS contains fivemain features:• presentation material—displays information on a screen of previously prepared

material

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• commenting—participants add comments on topics or ideas previouslygenerated by other participants

• brainstorming—participants add comments anonymously• voting—participants use the computer to vote on a topic• evaluation—ranks the alternative decisions based on the preferences of the

participants.GDSSs are an emerging trend rather

than common practice in business. IBMhas been using GDSSs, and they havereduced the length of meetings andallowed people to focus on the particulartopic. The brainstorming feature of aGDSS encourages participation byallowing ideas to be entered anonymously.However, it often increases conflict, aspeople are more assertive. For example, aGDSS makes it possible to tell the bossthat he or she is incorrect without fear ofretribution.

Responsibility for decisionsResearch into artificial intelligence led to the development of intelligent DSSsbased on neural networks and expert systems. This provided a class of DSSs thatcould replicate an expert’s knowledge and could learn from experience. More andmore tasks are being done by expert systems, including preparing tax returns,writing wills and diagnosing diseases. However, this increasing dependence onmachine intelligence raises new issues. Who is responsible for these automateddecisions? Do users of these expert systems also require knowledge in the area?Who would be at fault when a wrong decision is reached as a result of using a DSS?

There are four participants involved in the development and use of an expertsystem: the expert, the knowledge engineer, the professional who uses it, and the person who is affected by the decision. The problem can be caused by any ofthe participants. The expert might have provided inadequate knowledge, theknowledge engineer might have built the expert system poorly, the user mighthave applied the system incorrectly, or the affected person might have suppliedthe wrong data. An expert system is only as accurate as the expert and theknowledge engineer have made it. It will only consider the alternatives thought ofby the expert. It is important to remember that a DSS only provides advice. It isthe responsibility of the user to make the final decision.


1 What is an intelligent system?

2 Why is it important to preserve an expert’s knowledge?

3 How can a DSS result in a loss of expert knowledge?

4 Describe a common problem with decision-making.

5 How are DSSs used in unstructured situations?

6 How can erroneous inferences come from data mining?

7 Describe the issue of privacy in terms of data mining.

8 What is a GDSS?

9 Describe the five main features of a GDSS.

10 List the advantages for IBM of using a GDSS.

11 Who is responsible for decisions in the use of an expert system?

LEARNING ACTIVITIES

1 The manager of a $100 million pension fund used a neural network instead ofcommon stockmarket indicators to make investment decisions. When the neuralnetwork suggested that the fund should invest 40% of its assets in bank stocks,the manager overruled it. In retrospect, the neural network was correct. Explainwhy this experience should or should not convince people to overrule a neuralnetwork.

2 ‘The recent advances in technology should make it possible to protect anindividual’s privacy.’ Discuss this statement.

3 Fingerprint analysis is part of the science of biometrics, that is, the statisticalmeasurement of biological characteristics. Recently biometrics has been used infraud detection. Use the Internet to research other applications of biometrics.Does biometrics have the potential to invade our privacy?

4 You are a passenger on an aeroplane and have just learned that it will be landingautomatically, using an expert system. How would you feel about this situation?Give reasons for your answer.

5 What are an individual’s privacy rights in New South Wales? (Hint: Visit the PrivacyCommissioner’s Web page.)

Exercise 5.7



1 Which of the following is used tohandle uncertainty in a DSS?A fuzzy logicB conflict resolutionC data matchingD spreadsheets

2 An inference engine is something that:A is required in any artificial intel-

ligence applicationB produces the rules and inferences

found in an expert systemC acquires the knowledge required to

populate the knowledge baseD is the part of the expert system that

carries out the reasoning

3 Knowledge engineering is:A the art of designing and building an

expert systemB the process of determining a con-

clusion from a given set of factsC the art of designing and building a

neural networkD building a collection of knowledge

4 The three main components of a DSSare:A inference engine, model manage-

ment, explanation mechanismB data management, model manage-

ment, dialogue managementC model management, dialogue man-

agement, databaseD data management, database, user

interface

5 Decision support systems:A help users make decisions in struc-

tured situations

B are needed to solve all problemsC need not be interactiveD help users solve problems in semi-

structured situations

6 Heuristics:A are supplied by experts in an expert

systemB are a basis for queries in a relational

databaseC are used in spreadsheet modelsD are the same as algorithms

7 An intelligent agent could be used to:A search expert systems for the right

informationB train neural networksC filter emailD solve problems

8 Fingerprint matching as performed byan AFIS:A takes days to find a matchB still requires an expert to make the

final decisionC is an incredibly labour-intensive taskD will replace DNA matching

9 MYCIN is:A a famous medical neural networkB the first fingerprint-matching expert

systemC a system that can replace doctorsD an aid to diagnosing blood infections

10 A GDSS is a system that:A makes decisions for managersB always uses video-conferencingC is based on certainty factors and is

interactiveD assists users to make a decision by

working together in a group

184 Options

Chapter review


PART B


Statements

1 A piece of software to search throughrelational databases for relevant data.

2 A process of finding relationships andpatterns in the data stored in a database.

3 An information system that assist usersto make a decision.

4 Depends on a method to reach adecision but the correct decision is notguaranteed.

5 A rectangular grid made up of rows andcolumns to organise and store data thatrequires some type of calculation.

6 An inference strategy where the usersupplies all the data before thequestion is asked or the inference ismade.

7 Starts with one or more possiblesolutions and searches back throughthe system to determine the questionsto be asked.

8 Provides information and solves prob-lems that would otherwise require aperson experienced in that field.

9 An information system that works likethe human brain and is capable oflearning.

10 A database that collects informationfrom different data sources.

11 A ready-made expert system exceptthat it contains no knowledge.

12 An information system that assists usersto make a decision by working togetherin a group.

13 A set of general facts and if-then rulessupplied by an expert.

14 Describes the variables that exist be-tween a ‘true’ and a ‘false’.

15 Does not use a method to reach adecision.

16 An information system that receivesdata from the environment, reacts tothat data and produces an intelligentresponse.

List of terms

a backward chaining j knowledge base

b data mining k expert system

c data warehouse l GDSS

d DSS m neural network

e expert system shell n semi-structured

f forward chaining situation

g fuzzy logic o spreadsheet

h intelligent agent p unstructured

i intelligent system situation

PART C


1 Briefly describe four different types ofDSSs.

2 A medical diagnostic DSS can assist adoctor by providing a patient diagnosis.It must be able to explain to the doctorhow it reached that diagnosis. Do youthink an expert system or a neural net-work is suitable for this situation? Givereasons for your answer.

3 Explain the difference between thefollowing terms:a forward and backward chainingb structured and unstructured situ-

ationsc database of facts and knowledge

base.

4 Describe some of the analysis toolsprovided in a spreadsheet.

5 Neural networks have to be ‘trained’.What does this mean and why is itnecessary?

6 Identify a social or ethical issue involvedin DSSs. Identify both the positive andnegative aspects of the issue.

66AUTOMATEDMANUFACTURINGSYSTEMS

cchhaapptteerr









Outcomes

This chapter examines the characteristics ofautomated manufacturing systems. It inves-tigates specific examples and reasons forautomation. The information processes of anautomated manufacturing system and the socialand ethical issues that relate to these systemsare presented.

Overview

Automated manufacturing systems

6.1 Characteristics of automatedmanufacturing systemsAutomation refers to the application of automatic control to industrial processes.It refers to the application of machines to tasks once performed by human beings.The development of automation has become increasingly dependent on the use ofinformation technology.This has resulted in automated systems that have becomeincreasingly sophisticated and complex. Advanced automation systems representa level of capability and performance often greater than what people couldachieve. Automation is a term used widely in a manufacturing context.

187

During the Industrial Revolution, products were still custom-made withmanually operated machine tools. The automation concept of the assembly linebecame a reality in the twentieth century. It resulted in better and cheaper goods and services.These automated manufacturing systems out-produced humanworkers. Since the 1950s, a great number of scientific and technologicalbreakthroughs have occurred. One of the most important developments was theinvention of the digital computer. This invention, coupled with the concept ofcomputer control, has made possible the present-day automated manufacturingindustry.

Manufacturing is the process of producing a product that meets a specificneed.A strong manufacturing industry is necessary for strong economic growth inthe modern world. To maintain a strong manufacturing base, it is necessary toproduce high-quality products from this base. The products must be as cheap aspossible while still maintaining a high level of quality. Automated manufacturingsystems aim to provide these benefits.

Automated manufacturing systemsAn automated manufacturing system is an information system involved inproduction by inventory tracking, record-keeping, production scheduling andactual production.The information technology employed in automated manufac-turing systems is divided into several uses. The first use is keeping track of aninventory and the location of products and parts.The second use is performing therecord-keeping about who did what work, when they did it, and how well theydid it. The third use is related to the actual production, including productionscheduling. Automated manufacturing systems have computerised controls built

IITT FFaaccttIT FactThe term ‘automation’ was used by D. S. Harder, an engineering manager atthe Ford Motor Company, in 1946. He used the term to describe theincreased use of automatic devices and controls in mechanised productionlines of the automobile industry.

188 Options

into the manufacturing equipment. Every part of the production is scheduled andperformed automatically. It requires automatic movement of material, precisescheduling and execution of all work steps, and automatic monitoring of qualityand safety.

An automated manufacturing system has the ability to perform the followingtasks:• Collecting data from the environment through a wide range of sensors. A

sensor is an input device that measures data from the environment, such astemperature, pressure, motion, flow and light.

• Processing data into information using a microprocessor as a controller. Acontroller receives data from a sensor and changes it into information that canbe used by the system. For example, sensors often collect data in analog form,and this needs to be converted to digital form for use in the system.

• Performing work on a product. In most cases, the product must be moved fromone location to another during the series of processing steps.At each processinglocation, the accurate positioning of the product is generally required.Actuatorsperform the actual work of the system, such as stopping a pump, moving aswitch or turning on a light beam. An actuator carries out a mechanical actionunder the control of a signal from a controller. Some common actuators areelectric motors, solenoids and stepping motors. (See Figure 6.1.)

Figure 6.1 Automated manufacturing system using robots.

Direct usersAutomated manufacturing industries employ a wide range of people withdifferent skills. Each employee has certain responsibilities in his or her job, and allemployees depend on information and data to perform their jobs satisfactorily.The organisation of most manufacturing companies is arranged in a hierarchy of responsibilities. This can help new employees to identify their position in acompany and the people to whom they are responsible (see Figure 6.2). Each


person employed by the company is dependent on the flow of informationthroughout the system. Some people in an automated manufacturing system areclassified as direct users.

189

Technical,R&D,

EngineeringFinance

Manufacturing/Factory

Procurement Secretarial(Managers)

Sales/Marketing

CastingDepartment

MachiningCell 1

MachiningCell 2

FinishingDepartment

AssemblyDepartment

(Supervisors)

(Managing Director)

(Board of Directors)

(Shareholders)

Lathe 1 Lathe 2 Grinder Drill Press (Operators)

ProductionPlanning Production Quality

(Managers)

Figure 6.2 Organisation chart of a manufacturing company.

The direct users are people who interact with or are in control of theautomated manufacturing system. They include both the people using themachines and the supervisors.The supervisors oversee the operation to ensure thatproduction does not get behind schedule. Direct users have a task that isdependent on the information produced during the manufacturing process. Theinformation in an automated manufacturing system might include the following:• number of parts needed for a product• number of employees and skills needed to produce the product• cost of parts• cost of production• sources of component parts• prediction of market need• time required to machine or process parts• number of finished products in stock.

190 Options

Block diagramsA system is a group of elements that work together to achieve a purpose. Systemsare used to understand and explain the world around us. A block diagram is adiagram used to represent a system. The system is shown inside a rectangle, andthe edge of the rectangle is the system boundary. Circles are used to representinputs and outputs that are external to the system. A circle with a line down themiddle is used to represent output from one system that is the input to anothersystem (see Table 6.1).

Symbol Meaning

I External input

System

O External output

External output/input

Table 6.1 Symbols used in a block diagram.

A system will take one or more inputs and perform a series of actions toproduce one or more outputs. At the simplest level, a block diagram consists of asingle input, a single output and a single system. The block diagram in Figure 6.3represents the manufacture of a system unit for a personal computer. The input is the components that make up a personal computer, such as the casing,motherboard and hard drive.The automated manufacturing system assembles theseparts using a computerised control. The output or product is the system unit.

AssembleParts

SystemUnit

ComputerParts Ι Ο

Figure 6.3 A simple block diagram for the manufacture of a system unit.


Refinement is examining a system in greater detail by breaking it down intosmaller parts. Each part is considered a system in itself, or a subsystem. Asubsystem is a small system that is part of a larger system. It also contains a groupof elements that work together to achieve a purpose. The block diagram in Figure6.4 shows the manufacture of a system unit containing a subsystem for themotherboard, hard drive and DVD drive.

191

InsertHard Drive

InsertDVD Drive System UnitInsert

Motherboard

Hard Drive DVD DriveMotherboard

Casing Ι Ο

Ι Ι Ι

Figure 6.4 A block diagram for the manufacture of a system unit showing subsystems.

1 What is automation?

2 What is an automated manufacturing system?

3 How is information technology used in an automated manufacturing system?

4 Describe three tasks performed by automated manufacturing systems.

5 Explain the difference between a sensor and a controller.

6 List three common types of actuators.

7 What are direct users of an automated manufacturing system?

8 What is the purpose of a block diagram?

9 List the symbols used in a block diagram.

LEARNING ACTIVITIES

1 Choose a common household product:a List the raw materials that go into its manufacture.b List the processes that would go into making this item.c Draw a block diagram to represent this manufacturing system.

2 Choose an automated manufacturing industry near you:a Describe this automated manufacturing system.b Identify the characteristics of this system.c Draw a block diagram to represent this system.

3 What is the role of accounting in manufacturing? How does an accountant in afactory depend on using a computer? What sort of information would theaccounting department need in a factory?

Exercise 6.1

192 Options

6.2 Examples of automatedmanufacturing systemsIn this section, we examine four examples of automated manufacturing systemsand the reasons for automation.

Specific examplesFour specific examples of automated manufacturing systems are assembly lineproduction, automated warehouses, CAD/CAM and mail sorting.

Assembly line productionAssembly line production is a series of workstations connected by a transfer systemthat moves parts between each workstation. Each workstation is designed toperform a specific processing operation, so that the product is gradually constructedas it progresses along the line. Raw materials enter at one end of the line, proceedthrough each workstation, and emerge at the other end as a completed product.Workstations are simultaneously processing a part of the product. One finishedproduct is produced with each cycle of the line. Assembly line production requiresvarious operations and product transfers to be properly coordinated. This iscontrolled by special computers called programmable logic controllers. PLCs arethe main process control computers used in manufacturing. They are used for datacapture and actuator control and to perform timing and sequencing functions.

Assembly line production isapplied in many industries, such asthe car industry (see Figure 6.5).A typical car has over 5000separate parts that need to beassembled to produce the final car.A large car manufacturer, such asMitsubishi or Ford, might employ3000 to 4000 employees in suchjobs as accounting, management,car assembly, warehousing andmarketing. Car assembly oftenrequires some products from othermanufacturers. An example wouldbe the alternator and electricalsystems used in a car. The carmanufacturer needs to keep adatabase on the quantity and stocknumber of each part so thatreordering from the warehouse isnot a problem. On the assembly

4 What are the different engineering professions that might be employed in anautomated manufacturing industry? Make a list of the jobs that they might do.

5 How is a database used in an automated manufacturing system? Draw a simpledata flow diagram to indicate the flow of data between the customer and thesystem.

Figure 6.5 Assembly line production.


line, information needs to be kept about production times, machine maintenance,faults in production and total number of cars produced over a set period. Carsneed to be labelled and packed for various destinations both interstate andinternationally. Assembly line production is very important in the car industry formaintaining good quality control, as well as for reducing the cost of production.

193

IITT FFaaccttIT FactAutomation was seen to be a valuable asset in the early 1930s when HenryFord produced his famous Model T car.

Automated warehousesAn automated warehouse uses automatic control for the storage of products (seeFigure 6.6). It is a very important aspect of modern businesses. Manufacturingindustries need to be able to store parts that are used to make up a final product,as well as to store products for future customer orders. The tracking of warehouseitems is necessary for the following reasons:• knowing when to reorder a part• monitoring the daily or weekly use of a part• knowing which products are not being sold• calculating capital tied up in warehouse stock• being able to assemble customer orders from warehouse stock• knowing what space is available for new product storage.

The above reasons have beeninfluential in the progress and devel-opment of automated warehouses.Automation has taken the form ofautomatic tracking by using barcodeson the products or parts in thewarehouse. By scanning an item’sbarcode and storing this informationin a database, it is possible to knoweverything about the product or part,as well as its storage location in thewarehouse. Automated warehousesuse machines independent of humanguidance for loading or unloading aproduct. These machines are con-trolled by a central computer linkedto the database. This computersystem is used to track products acrossmultiple warehouses that may beseparated from each other by largedistances.

CAD/CAMCAD (computer-aided design) is the use of information technology to design andanalyse a product or object. Designers working with a CAD system, rather than ona traditional drafting board, create the lines and surfaces that form the object and

Figure 6.6 Jobs such as this may become redundant aswarehouses become increasingly automated.

194 Options

store this model in the database. The CAD software allows the designer toperform various analyses on the object, such as heat transfer calculations. Thedesign is refined by adjustments made on the basis of these analyses. Once thedesign procedure has been completed, the CAD system generates the detaileddrawings required to make the product.

CAM (computer-aided manufacturing) refers to the specialised informationtechnology tools that automate the entire manufacturing process. A computersystem is used to automatically control the actions of the plant equipment. It isalso used to monitor the collection of data from the factory, the analysis of thedata, and the communication of results to management.

A CAD/CAM system involves not only the automation of the manufacturingoperations but also the automation of elements in the entire design andmanufacturing procedure. The combination of CAD and CAM has been appliedin many industries, such as machined components, electronics products andequipment design. CAD/CAM systems often use numerical control machines.

Numerical control (NC) is a form of programmable automation in whichnumbers control a machine.The initial application of numerical control was in themachine tool industry. It was used to control the position of a cutting tool relativeto the product part being machined. The numbers are coordinates in threedimensions that define the exact position of the cutting tool in relation to theproduct part. It then uses a program to sequence the coordinates that direct thecutting tool to machine the part. NC usually receives feedback from the system toensure the program has been correctly performed.

NC technology allows complex parts to be fabricated quickly and accuratelyby automated machine tools that directly drill, grind, cut, punch and mill to turnraw material into a finished product. NC machine tools use a numerical controlmethod for activating the tools in response to a predetermined command storedas digital data on tapes or in semiconductor memory. The programs have twofunctions: positioning the tool point in three dimensions relative to a product partand controlling secondary functions, such as speed, feeding, coolant flow, gaugingand tool selection.

There are basically three types of NC machine tools. The first is the con-ventional NC system where functions are wired together in a fixed pre-engineeredarrangement. The second is computer numerical control (CNC) in which amicroprocessor is programmed to control some or all of the NC functions. Thethird approach is direct numerical control (DNC) in which a group of NC (orCNC) machine tools are simultaneously controlled by a host computer.

Many applications of NC have been developed since its initial use to controlmachine tools. NC is used in electronic assembly, drafting machines that prepareengineering drawings, coordinate measuring machines that perform accurateinspections of parts, and flame cutting machines. In all these applications, codednumerical data is employed to control the position of a tool or workhead relativeto some object. The four advantages of NC machine tools over standard machinetools are:• one person can operate more than two NC machine tools• greater accuracy with better repeatability• the ability to process products that have complex shapes• shorter processing time.


Mail sortingMail sorting involves the collection, sorting and delivery of mail to various homesand businesses. In the early days of postal sorting and delivery, people sorted themail by hand, reading the addresses and sorting the mail into groups based oncities and towns. Once sorted into various destinations, the mail was thentransported to the city or town and then re-sorted to a final level for delivery tothe home or business. Mail sorting became easier with the advent of postcodes andmachine-stamped codes on envelopes. Today, automated mail sorting machinesaccept a wide variety of letters and parcels and have the ability to sort themquickly and efficiently. Automated mail sorting machines use optical characterreader (OCR) machines.

An example of an OCR machine is the Electrovision EV-40.The EV-40 is usedin high-volume outbound and incoming mail applications. The EV-40 is entirelysoftware based. If the EV-40 is installed in an automated mail-sorting machine, itscans 10 cm vertically, starting at the bottom of the mail piece, and 28 cmhorizontally. It optically reads and interprets four lines of the address block onmachine-printed mail. This information is converted to a barcode, and theenvelope is encoded with this barcode. This means that high-volume mailersachieve higher percentages of barcode mail, which leads to greater cost savingsand higher efficiency in mail operations.

The National Presort Inc NP-8000 is a machine that can sort up to 40 000 mail pieces per hour and handle small flat parcels as well. This machine allows a computer to monitor mail and check for changed addresses, as well as otheraccounting information, that can be used by various businesses.

Reasons for automationAutomated manufacturing systems are able to repeat their actions accurately. Forthe automobile industry, this means that quality control is maintained on all carsby the use of machines that do not tire on the production line. It is possible to runmachines for many hours at little cost, and this reduces costs associated with carmanufacture. This reduction in cost by the use of computer-controlled machinesalso applies to other industries. Theability of machines to run for longperiods of time on repetitive tasks at areduced cost also means productivitygains.

When designing new products ormodifying older products, computerscan be used to help automate thedesign process. The software used inCAD allows the user to make a virtualmodel in the computer. This modellingcan be used to simulate the sizes that aproduct may need to have or perhapsthe wear and tear that might occur in acertain situation. A simple examplemight be the design of a seat in a car.The computer can automatically, withthe help of an engineer, design a seatthat can then be simulated to see if itwill fit neatly into the car. It can also betested for proper movement fordifferent sized people. If the design is

195

196 Options

found to be unsatisfactory, then it is relatively easy to modify the design using theCAD package. This leads to design gains through simulation and modelling.

Another major advantage of automation is increased safety.Automated manu-facturing systems can protect people who must work in high-risk workingenvironments, such as welding car doors or operating a dangerous machine.Sensors can collect data about the operator’s position, as well as information aboutthe machinery and raw materials. A simple example would be a sensor detectingthat an operator’s hand is too close to a revolving shaft and automatically stoppingthe shaft, as well as signalling an alert on a display device. This information canalso be logged into a central database for later evaluation of safety features andtheir effectiveness. The information could also be used for aggregate safetystatistics on the machine floor.

Arco is a company that manufactures sauce-pans. The saucepans are made from platesteel in a factory. The design of the sauce-pan is done with the help of a CAD system.It stores the three-dimensional design of thesaucepan along with the relevant sizes ofsides, bases and lids; base thicknesses; andhole positions for the handles in a CADdatabase. The weight of each saucepan is automatically calculated by the CADpackage. This information is made availableto a DBMS. Data is required by:• finance employees to estimate the cost

for each saucepan and the necessarymark-up of the product

• marketing employees to describe thesize of the saucepan, as well as itscolour and handle shape if it has achoice of handle shapes

• pressing machine operators on thefactory floor to provide the thickness ofmaterial to be pressed by the machineinto the saucepan so that the sizes andtolerances can be set on the machine

• quality control employees to ensurethat the handles are fixed on properlyand will not shake loose, as well as toensure that the saucepan base is flatand won’t wobble on a stove

• customers (retailers) to know whatmaterials the saucepan is made fromand its life expectancy, as well as theprice.

The flow of data in this automatedmanufacturing system is important. It isused in different ways by different peopleand is obtained from a central database.The information is collected from differentpoints in the factory, including the design,finance, marketing and quality controlunits. On the shop floor, the data iscollected using a range of sensors andtransferred to the database. The sensordata from the production line is also usedto control actuators that will start motorsand other machinery to manufacture thesaucepan.

Case study Arco Saucepans

Automated manufacturing systems 197

1 Describe an assembly line production.

2 What is performed by a programmable logic controller?

3 How is assembly line production applied in the car industry?

4 What is an automated warehouse?

5 Explain the difference between CAD and CAM.

6 What is numerical control?

7 List the three types of NC machine tools.

8 Outline four advantages of NC machine tools over standard machine tools.

9 Why are automated mail-sorting machines used?

10 List some of the reasons for automation.

11 How does automation achieve increased safety?

12 The following questions relate to the Arco Saucepans case study:a What is stored by the CAD system?b List the people who require data from the database.c Describe the flow of data in this automated manufacturing system.

LEARNING ACTIVITIES

1 Automated manufacturing systems perform information processes requiringparticipants, data/information and information technology. Clearly identify theparticipants, data/information and information technology for the followingautomated manufacturing systems:a assembly line productionb automated warehousec CAD/CAMd mail sorting.

2 Discuss the relationships between participants, data/information and informationtechnology for the following automated manufacturing systems:a assembly line productionb automated warehousec CAD/CAMd mail sorting.

3 Outline the reasons for automation in each of the following automated manu-facturing systems:a assembly line productionb automated warehousec CAD/CAMd mail sorting.

4 What cars are assembled in Australia? Are all the parts made in Australia? Identifyten parts that go into building a car. Briefly outline the advantages and dis-advantages of the same company manufacturing every part of a car rather thanbuying parts from other manufacturers.

Exercise 6.2

198 Options

6.3 Collecting in automatedmanufacturing systemsCollecting for an automated manufacturing system involves using CAD/CAM,sensors, barcode readers and analog-to-digital conversion.

CAD/CAMCAD/CAM is the use of computers to perform many of the functions related todesign and production. It is based on the ability of a computer system to process,store, and display large amounts of data representing both part and productspecifications. CAD refers to the use of information technology to design andanalyse a product. CAM refers to the specialised information technology tools thatautomate the entire manufacturing process. The CAD/CAM system can beregarded as a flow of information from the design workstation to the database andthen from the database to the factory machinery (see Figure 6.7).

SPECS

CAD

Geometric Modeling

Analysis

InteractiveTerminal

Product Specifications

Automated Drafting

CAM

Numerical Control

Robotics

DataBase

Process Planning AutomatedFactory

Factory Management

Figure 6.7 CAD/CAM relationship through a common database.

A CAD system requires a high-performance computer with specialised CADsoftware and a plotter. The CAD software is made up of different softwaremodules that carry out specific tasks, such as circuit analysis or three-dimensionalsolid modelling. The CAD software stores the designs and provides data for a


database. This data consists of product specifications, such as plate thickness,number of screws needed, size of sheet metal base, weight of product and overalldimensions for packaging. The information from the CAD system stored in thedatabase is used by the CAM system. Some of the commonly available functionsprovided by CAD software are:• image manipulation—add, delete and edit images• transformations—rotate, translate and scale images• libraries—store standard and customised drafting symbols• file management—create, merge and delete image files.

Automated manufacturing sys-tems use the data supplied by aCAD/CAM system for other func-tions in the organisation. A CIM(computer-integrated manufactur-ing) system includes all the engi-neering functions of CAD/CAMplus the business functions of theorganisation. The business func-tions include order entry, costaccounting, employee payroll andcustomer invoicing. CIM involvescomputerised data collection andintegrated flow of data betweendesign, manufacturing and plan-ning. It applies information tech-nology to all the operational andinformation processing functions.CIM has benefited by recent tech-nical advances, such as increasedcomputer power, better data man-agement and faster communi-cations. CIM represents the highest level of automation in manufacturing.

SensorsSensors are input devices that measure data from the environment. They convertinput provided by the environment into a signal that can be communicated to acontrol program. Recent advances in technology have provided a vast array ofsensors, such as highly sensitive electromechanical probes, scanning laser beamsand machine vision. Machine vision, which requires the processing of largeamounts of data, can be accomplished only by high-speed computers. It is beingused for many manufacturing tasks, such as part identification, quality inspectionand robot guidance.

Sensors are sometimes referred to as transducers because they convert onephysical quantity into another. They often generate a potential difference, orvoltage. For example, a tachometer is a rotational speed sensor that convertsvelocity into a voltage.A good sensor needs to rate highly on the following criteria:• accuracy—the difference, if any, between the value of the measured variable

and the measurement obtained by the sensor• resolution—the level of change to which the sensor will respond by changing

its output

199

Figure 6.8 Computer-integrated manufacturing.

200 Options

• repeatability—the variation, if any, shown by the sensor over repeatedmeasurements of a given value

• range—the upper and lower limits of the sensor’s measurements• dynamic response—the maximum frequency of change in a measured variable.

IITT FFaaccttIT FactSensors are used by robots to inspect the manufacturing process. They deter-mine whether each machine part is consistent with quality specifications.

Sensors are used to detect different physical conditions, such as temperature,pressure, motion, flow and light.

TemperatureTemperature sensors are devices that measure the temperature of the air, a fluidor an object. The control of temperature is very important in many industries.Different temperature sensors are required for different applications. Somesensors would be inappropriate due to the range of temperatures they detect, theirsensitivity or their fragility. Temperature is detected using the resistance of aconductor. When the temperature rises or falls, the resistance of the conductorincreases or decreases. The three main types of temperature detectors are theresistance thermometer, the thermocouple and the thermistor.• Resistance thermometers measure temperature using a metallic conductor,

such as copper, nickel or platinum. The conductor’s resistance to electricalcurrent increases with temperature. The metal is either wound as a coil ordeposited as a thin film onto some suitable material called a substrate.Resistance thermometers are available for temperatures that range from 200°Cto 800°C.

• Thermocouples measure temperature using two different metals (a couple) inelectrical contact. A voltage is produced that is proportional to their tem-perature difference. The point at which the two different metals meet is calleda thermojunction. The thermocouple has two such junctions: one held at areference temperature and the other in contact with the temperature sourcethat needs to be measured. A temperature difference has to be provided tomake a thermocouple work.The temperature range for thermocouples is quitelarge, being from 250°C to 1400°C.

• A thermistor (thermal resistor) is a semiconductor device that measures tem-perature in a manner similar to a resistance thermometer.The resistance of thesemiconductor in a thermistor is very rapid. This makes thermistors moresensitive than resistance thermometers to small changes in temperature.

PressurePressure sensors are devices that measure the exertion of a force. Pressure in apipe or container can be sensed by using a pressure gauge. The gauge is designedin such a way that the liquid or gas that is being measured is connected to a curvedtube.The higher the pressure, the more the tube is forced into a straight line fromits initial curved position. The amount of movement is turned into a voltage byusing a variable resistor called a potentiometer.This resistor has an electric current


passing through it, and the difference in voltage can be detected as the resistancechanges. This voltage is then used to register the pressure. The same effect can beobtained by using a diaphragm.

A diaphragm is usually a small circular piece of material held inside a smallcontainer with one surface in contact with the liquid or gas being measured andthe other exposed to normal air pressure.A diaphragm is made of flexible materialthat will move different amounts according to the pressure on one side of thediaphragm. This movement is converted into a voltage in a manner similar to the one mentioned above. In some diaphragm devices, the diaphragm is directlyconnected to a piezoelectric material, and the voltage is generated by the pressurebeing applied to the material. This voltage is then passed as a signal back to thecomputer.

MotionMotion sensors, or velocity sensors, are devices that measure the rate of change ofposition. They calculate how far an object has moved from a starting position.They use electromagnetic induction to produce a voltage proportional to thevelocity of a conductor (wire) moving in a magnetic field. The device consists ofan armature with fixed magnets around it like an electric motor. Rotation of thearmature produces an induced current in the windings and a voltage proportionalto the rate at which the conductor is being rotated.

Acceleration sensors depend on the piezoelectric properties of materials, suchas quartz or ceramic crystals. A crystal is attached to the base of a mass. As a forceis applied to the crystal and then onto the mass, a small electric current isgenerated in the crystal due to the strains that are set up.

FlowFlow sensors are devices that detect the motion of fluids, including liquids andgases. They are often used to measure the flow of liquids and gases through pipesand drains. One method of detecting a flow of liquid is to have the liquid turn asmall paddle wheel just like an old water wheel. The speed with which the wheelturns gives a measure of the flow of the liquid. The wheel is attached to atachometer, and the voltage generated by the tachometer is proportional to theflow of liquid. Another type of flow sensor uses an ultrasonic signal to detect thechange in frequency of the returned signal due to the interference of the passingliquid or gas. The change in frequency is converted to a voltage or currentproportional to the flow of liquid or gas.

LightLight sensors, or optical sensors, are devices that can detect changes in the level oflight.They are used in industrial processes to detect imperfections in products. Forexample, in steel milling, light sensors detect irregularities in the rolled steel as itpasses along the rolling mills. Light sensors are used to control the motion ofrobots and their interpretation of the environment. Researchers are working veryhard at interpretation of light images received by various detectors. The two mainproblems associated with light sensors on robots are:• High bandwidth.The large amount of data to be transferred requires very high

frequencies. The higher the frequency of the bandwidth, the more bits persecond that can be transmitted.

201

202 Options

• Enormous amount of processing. Each piece of data or pixel contained in thepicture requires calculations to determine whether it is part of an object.These problems do not arise in simple optical devices used for brightness

detection. These devices may only detect differences between black and white,such as the dark lines and white spaces in barcodes. The development of solid-state optical sensor arrays has reduced both costs and processing requirements.Anexample of these light sensors is a photodiode.

A photodiode produces a voltage in proportion to the amount of light fallingon its surface. The most common use of photodiodes is as a light-beam switch. Asource of light is placed to strike the diode; and if the beam is interrupted, thevoltage of the diode falls. This device can be used for many applications that needto detect when an object is present or not present. A simple example would bethe detection of customers walking into a shop. In an automated manufacturingsituation, the computer might wait for a break in the light beam to signal that apart has moved onto a conveyor belt or near a robot. The computer would thensend a signal to the robot or to another machine to cause some action to happen.

Images from the outside world can be detected by the use of a two-dimensionalarray of solid-state devices called charge-coupled devices (CCD). A two-dimensional CCD is made up of a grid of photosensitive elements. The more lightat each location in the grid, the more electrical charge. CCD devices are made intovery robust and accurate cameras for use on robots and in industry. CCD cameras:• work at low voltages and have only a small power requirement• are very accurate at positioning objects• are not damaged by intense light• are sensitive over a wide spectral range (light range)• do not have memory and so moving objects are not smeared.

Barcode readers and inventory trackingBarcode readers are input devices that allow acomputer to read barcodes found on productsor parts (see Figure 6.9). The barcodes containinformation about the product or part. Thisinformation is needed by managers to trackhow many products are available to sell andhow many parts are available for use in manu-facturing the products. The total number ofproducts or parts held is called an inventory.This information is vital if the factory is not torun out of components that go into the finishedproduct and thus delay production. It also helpsthe managers determine how quickly productsare selling and whether a suf-ficient quantityhas been scheduled for manufacturing. Themajority of companies label parts and productswith barcodes.The use of barcodes enables easytracking of the parts through the factory as wellas easy warehousing of parts and products.A barcode is represented by a pattern of wideand narrow bars. The barcode reader scans thebars and translates the different patterns backinto regular characters and sends them on to a

Figure 6.9 Barcode reader.


computer for further processing and storage. The processing might involvecalculating the cost of an item, as in supermarkets, or making a decision aboutthe item, such as whether to machine it or stack it in box.

203

IITT FFaaccttIT FactBarcodes were first developed for U.S railways to keep track of whichcarriages went with which engine. The barcodes were imprinted at auniform height above the ground on the side of railway carriages that wentwith a particular ‘system’. The barcodes of the different carriages could thenbe read to compile information on particular groupings of carriages.

Every barcode starts with a special start character and ends with a special stopcharacter. These codes help the barcode reader detect whether to start scanningforward or backwards. Some barcodes may include a checksum character justbefore the stop character. When the barcode is printed, a checksum is calculatedfrom the characters in the barcode. The barcode reader performs the samecalculation and compares its answer to the checksum it read at the end of thebarcode. If the two numbers don’t agree, then the barcode reader will try to readthe barcode again.

There are different barcodes, each with its own particular pattern of bars. Forexample, the UPC-A code is used in retail in the USA, has twelve numeric digits,and identifies the manufacturer and particular product. Other codes, such asCode39 and Code128, include upper-case and lower-case letters, digits and a fewsymbols. EAN-13 is the code used in Australia, as well as other countries, formarking retail goods. It consists of thirteen digits: the first two or three are acountry code, followed by nine or ten digits and a single-digit checksum.Supplementary two-digit and five-digit barcodes are sometimes added to thecode. Each participating country has EAN barcoding authorities that regulate the use of retail barcodes.

The last digit in the EAN barcode is a checksum and is a modulo-10calculation. The algorithm to calculate the checksum is given below:1 Add the values of the digits in the even positions (positions 2, 4, 6 etc.).2 Multiply this result by 3.3 Add the value of the digits in the odd numbered positions (positions 1, 3, 5

etc.).4 Sum the results of steps 2 and 3.5 The check digit is the smallest number that, when added to the result in step

4, produces a multiple of 10.

For example, to find the checksum for the barcode 012345768901:1 1+3+5+6+9+1 = 25 (adding the digits in the even positions).2 25×3 = 75 (multiplying the result by 3).3 0+2+4+7+8+0 = 21 (adding the digits in the odd positions).4 75+21 = 96 (adding the results of steps 2 and 3).5 96+x = 100 (finding the smallest number that, added to the result in step 4,

will produce the nearest multiple of 10).

Therefore, the check sum is 4 (96+4 = 100).

204 Options

Analog-to-digital conversionData collected from sensors is often in analog form, and this needs to be convertedinto digital form so it can be used by a digital computer. A device used to changeanalog into digital is called an analog-to-digital converter (ADC). Data may alsoneed to be converted from digital back to analog. A digital-to-analog converter(DAC) is a device that converts a digital signal into an analog signal. Most ADCsare also DACs.

An ADC takes an analog signal, such as a voltage or electric current, andelectronically converts it into digital data. The digital data comprises a number ofbits, such as eight, sixteen, thirty-two or sixty-four. The more bits that are used,the more expensive the ADC. For example, a temperature sensor might measurea range of temperatures from 0°C to 100°C using a voltage range from 0 to 5 volts.If the temperature is 40°C, a voltage of 2 volts will be produced. The computerstores its data in a byte made up of eight bits, and a range of values from 0(00000000) to 250 (11111010) can be used. The ADC must change a voltagerange of 0 to 5 into a value range of 0 to 250. The mathematics required involvesdividing the voltages by 5 and multiplying the result by 250 (see Table 6.2).

A reading of 2 volts from the temperature sensor is converted to a decimalnumber of 100 or a binary number of 01100100 inside the computer. It isimportant to note that the temperature is only measured to the nearest 0.4°Csince digital devices are restricted to discrete quantities, in this case 0 to 250. Forexample, 1°C would be represented by 0.05 volts, but this voltage converts to 2.5and cannot be represented as a discrete quantity on a digital scale of 0 to 250.

Temperature (°C) Volts Decimal Binary0 0 0 00000000

0.4 0.02 1 00000001

0.8 0.04 2 00000010

1.2 0.06 3 00000011

1.6 0.08 4 00000100

2.0 0.10 5 00000101

: : : :

19.6 0.98 49 00110001

20 1.00 50 00110010

40 2.00 100 01100100

60 3.00 150 10010110

80 4.00 200 11001000

: : : :

99.6 4.98 249 11111001

100 5 250 11111010

Table 6.2 Analog-to-digital conversion for the example temperature sensor.


DampingDamping is a decrease caused in the amplitude of successive oscillations or waves. For example, shock absorbers in a car are a damping device. They restrainthe motion of the car’s springs so that the expansion and contraction of the springsdo not shake the car excessively. When applied to automated manufacturingsystems, damping is the process that modifies the signal to the output devicebased on the input signal. Signals are received from a sensor, the controller changesthese signals into information, and the actuator carries out some action. The rateat which a system responds to the controller is very important, and dampingdevices help to determine that response rate. There are three types of damping(see Figure 6.10):• Overdamping occurs if the change is too slow, and the actuator takes longer to

reach the desired level or position. However, overdamping does not overshootthe desired level. It is a slow reaction to change and return to stability.

• Underdamping occurs if the change is too fast, and the actuator overshoots thedesired level. Underdamping then causes a return movement that will also betoo quick, causing the actuator to undershoot the desired level. Underdampingis a quick reaction to change resulting in rapid fluctuations before stability isreached.

• Critical damping is the preferred rate of change in the output of the system.The desired level is achieved in the quickest amount of time. Critical dampingis a quick reaction and a quick return to stability.

205

Initial

Final

Time

Measuredquantity Critical damping

Initial

Final

Time

Measuredquantity Overdamping

Initial

Final

Time

Measuredquantity Underdamping

Figure 6.10 Damping.

206 Options

1 Describe a CAD/CAM system.2 List some of the functions commonly provided by CAD software.3 Describe CIM.4 What is a sensor?5 Describe the three main types of temperature sensors.6 How does a pressure gauge work?7 What is calculated by motion sensors?8 Describe the two main problems associated with light sensors on robots.9 What is a photodiode?

10 Describe the use of barcodes in a factory.11 Calculate the checksum for the barcode 108976453811.12 What does an ADC do?13 What is damping?14 Which type of damping is the preferred rate of change?

LEARNING ACTIVITIES1 Aeroplanes are fitted with an automatic cruise control that keeps the plane at a

steady speed.a Draw a block diagram of this system showing the flow of data within the system

and the sensors required.b Describe the operation of one sensor that would be needed in the cruise control

system.c Describe the effect of underdamping in this system.

2 Collect some barcodes from various objects. What do you notice about the firstcharacter? The second character? If the barcode has 13 characters, check thechecksum using the algorithm presented in the text.

3 Pick two examples where damping can be seen. Describe for each example whatthe effect of overdamping, underdamping, and critical damping would be.

4 A sensor measures temperatures from –20°C to 30°C using voltages ranging from0 to 5 volts. Convert the following temperatures into bytes (range from 0 to 250)that the computer can understand:a 30°Cb –10°Cc 0°Cd 20°C

5 Suppose you had to get a computer to make a measurement of a voltage thatranged from 0 volt to 200 volts. Assume that the ADC used 8 bits to encode therange, using a value range of 0 to 250. a What would the digital 8-bit reading for 160 volts be?b What would the digital 8-bit reading for 100 volts be?c What would the digital 8-bit reading for 20 volts be?d How accurately could the computer read a voltage?e How would the accuracy increase with a 16-bit ADC?

6 Use a CAD software package to design a personal computer.

Exercise 6.3


6.4 Other information processesAll information processes play a role in automated manufacturing systems,including processing, displaying, and transmitting and receiving.

ProcessingProcessing data for an automated manufacturing system is the manipulation of thedata.After the data is collected, it must be converted into a form for transmission.This process involves mass production and types of production.

Mass productionMass production is the manufacture of products in large quantities by standard-ised mechanical processes. It is based on four basic principles:• Production is divided into specialised tasks that are relatively simple and highly

repetitive.• Standardisation of parts, such as dimensional tolerances, allows parts to be

readily fitted to other parts without adjustment.• Specialised machines, materials and processes minimise the amount of human

effort and maximise the output.• Systematic planning of the total production process permits the best balance

between human effort and machinery.The principles of mass production have led to lower costs and major improve-

ments in uniformity and quality. Large volumes and standardisation have allowedstatistical control and inspection techniques to monitor production and controlquality. Mass production is used to manufacture a range of products, such as cars, televisions, refrigerators and kitchenware. Individual parts of these products,such as batteries and refrigerator compressors, may also be mass-produced. Theworkforce in mass production is usually semi-skilled for machine operation andassembly. Industrial robots are used in many mass production industries.

Inflexibility is a major problem of mass production. Maximum efficiency isachieved by using specialised tools, standardised parts and a very structuredprocess. Redesigning a product is expensive, as the new design may make the oldtools and machinery obsolete. Organisations are now using machinery with built-in flexibility. For relatively little extra cost, the tooling can be changed to adaptthe machine to accommodate changes in design. In addition to allowing greaterflexibility, this machinery provides opportunities to make customised products.There is a trend towards customising a product to meet the needs of individuals.It is an attempt to retain the advantages of mass production while providingcustomised value.The manufacturer regards the product as mass-produced, whilethe customer regards the product as customised.

207

IITT FFaaccttIT FactEarly cars were mass-produced with every unit identical to every other unitin all aspects, including their colour, which was black.

208 Options

Types of productionThe three types of production used in automated manufacturing systems arecontinuous, batch and discrete.

Continuous systems are capable of operating 24 hours per day for weeks ormonths without stopping. Specific times are set aside for maintenance and fine-tuning of the manufacturing system. The manufacturing equipment used for acontinuous system is specially designed for the individual industry and its product.The product being made is often required in bulk form with the output measuredby volume or weight. Continuous systems are often used in chemical manu-facture, food production and the processing of certain basic metals. In theseoperations, the products are processed in gas, liquid, or powder form to allow theflow of the material through the various steps of the production cycle.

A batch system is a discontinuous system that produces a specific quantity ofa product. The quantity of the product is called a batch run, or production run.Batch runs may produce several dozen to thousands of units of a product.A batchrun may have to be repeated at a later time. Batch systems are used to manu-facture different types of products using the same manufacturing equipment.Consequently, the manufacturing equipment in a batch system must be muchmore flexible than that in a continuous system. To provide flexibility, workers ina batch system will need to be more highly skilled than workers in a continuoussystem. Metals are typically produced in batches rather than continuously as it isgenerally more difficult to handle metals in bulk form.

For each new batch, the manufacturing equipment must be reprogrammed andchanged over to accommodate the new product. The time required for thischangeover is a disadvantage of batch systems. It is lost production time. However,the variety of products in batch systems is limited, and the changeover ofequipment can be done very quickly. In a large batch manufacturing system, thereare often control and scheduling problems because batch runs are needed fordifferent products, with different customers and at different delivery times. Batchsystems require a coordinated approach to material ordering, warehousing andpart machining. Information systems can be a useful tool for solving theseproblems. Batch systems are used to make such products as spare parts for aircraft,cars, trucks and construction equipment.

A discrete system is a discontinuous system that performs a single task in asmall time interval. It produces items made to a customer’s exact specification andis sometimes called ‘jobbing’. Discrete systems use general-purpose machines,such as lathes and hand tools. The workforce is more highly skilled to make veryspecific products. Discrete systems manufacture products with the highest unitcost. Examples of products made with discrete systems include space satellites,ships, oil rigs and special-purpose manufacturing equipment.

Products are often made using a combination of continuous, batch and discretesystems. For example, a large ship is the only one of its kind, and this implies adiscrete system. However, the steel plates in the hull are produced by continuouscasting and rolling in a steel mill. They are made using a batch system.

DisplayingAutomated manufacturing systems display information by performing some work on the product. They use specialised display devices called actuators andmay have to convert data from digital to analog so that the actuators can performtheir tasks.


ActuatorsAn actuator is a display device that performs a mechanical action under thecontrol of a signal from a controller. Actuators perform the actual work of thesystem. Some common actuators are solenoids, electric motors, stepping motors,relays and hydraulic pumps.

209

IITT FFaaccttIT FactA ‘cell’ is an autonomous manufacturing unit that can produce a finishedproduct. Control at the cell level involves scheduling of individual parts onto machines.

A solenoid is a coil of wire around a movable magnet (see Figure 6.11). When anelectric current passes through the wire, a magnetic field is generated that will movethe magnet in the centre of the wire coil in one direction or the other depending onwhich direction the current is going.Washing machines use a solenoid to control thelevel of water entering the tub. The solenoid is attached to a small valve, which canbe opened or closed depending on the electric current in the solenoid.

Degree of movement On/off electric

current

Solenoid coilIron rod core

Figure 6.11 Solenoid.

Electric motors are clean and capable of high precision if operated carefully.Electric direct-current (DC) motors are very popular actuators because of theirease of use. DC motors run continuously, first in one direction and then in theother direction. The motion remains smooth and continuous. There is noparticular inherent control of position in DC motors. DC motors develop largetorques.Torque is the shaft-turning power that a motor can output. A high torquemeans that the shaft can move a load easily. An example of a high torque valueused in an antisocial way is the spinning of car wheels at traffic lights.A DC motorcan have its direction changed by reversing the current in its electric windings.This can be done by a relay or by power amplifiers electronically switching thedirection of current flow. DC motors are capable of high precision, fastacceleration and high reliability, making them good candidates for converting anincoming signal into mechanical motion.

Stepper motors are used in robots when precise open-loop control is needed.Open-loop control means that the desired position is calculated and then thedevice, or system, is told to go to that position. A stepper motor allows this tohappen easily. It is capable of being told to rotate through a number of degreesand then stop. It can rotate in either direction, just as a DC motor can, but it stops

210 Options

after a very accurate number of degrees. For example, a stepper motor can beinstructed to rotate exactly 20 degrees to the right and then 120 degrees to theleft.A disadvantage of the stepper motor is that it has a low torque compared witha DC motor and usually takes up more space than a DC motor. This means that,if a robotic device needs to move heavy loads, a stepper motor is not a goodchoice. Another disadvantage is that stepper motors accelerate and decelerate ateach step and therefore do not provide a smooth and continuous motion.

A relay is a switching device. It is primarily used when a small electric currentis used to turn on or turn off a large electric current. The device is made from asolenoid in which the movable magnet is connected to a mechanical switch, whichis held in a default position by a spring. When an electric current passes throughthe coil, the magnet moves against the spring and causes the switch to either openor close. The switch is usually connected to a more powerful electric source thanthe activation current for the coil. This means that a small voltage can control amuch larger current or voltage switch. This also means that the signal currents canbe isolated from a much more dangerous current grid. Sometimes many differentswitches may be connected to the moving magnet in the coil, and this allows onerelay to control many motors or other electric devices.

Hydraulic pumps are used when great strength is needed. A hydraulic fluidpowers the pump, or actuator. Hydraulic fluids are non-compressible fluids, suchas oil, that can be used in very high-pressure situations. The power transmitted bythe hydraulic fluid comes from the pressure the fluid exerts against things and notfrom compression of the fluid itself. The power from a hydraulic pump istransmitted through high-pressure tubing to a hydraulic device and then returnedto the fluid supply tank.

Digital-to-analog conversionDisplaying data may require converting digital data from the computer systeminto analog data for an output device. A digital-to-analog converter (DAC) is adevice that converts a digital signal into an analog signal. For example, thecomputer might be connected to an actuator, such as an electric motor. Thiselectric motor might be designed to accept voltages ranging from 0 to 10 volts.Therefore, the DAC could convert the digital signals in the range 0 to 250 intovoltage values from 0 to 10. The mathematics required involves dividing thedecimal number by 250 and then multiplying the result by 10. These calculationshave been approximated in Table 6.3.

Binary Decimal Volts00000000 0 0

00000001 1 0.04

00000010 2 0.08

00000011 3 0.12

00000100 4 0.16

: : :

11111001 249 9.96

11111010 250 10

Table 6.3 Digital-to-analog conversion for the example electric motor.


If the computer sends a signal of 11111010, it is converted into a voltage of 10 volts in the electric motor.

Transmitting and receivingIn automated manufacturing systems, the transfer of data and informationinvolves a signal.A signal describes the physical form in which data is transmitted,such as pulses of electricity in a wire or pulses of light in a fibre-optic cable. Signalshave a physical value that can be sensed and moved from one place to another.Sensors often generate a very weak signal. This requires the signal to be modifiedbefore a controller can use it. Signal conditioning is the modification of a signal fornormal usage. Amplification is a common signal conditioning technique thatmodifies a signal by increasing its strength.

NoiseSignals are affected by noise. Noise is unwanted data or interference that reducesthe quality of the signal. It is often the result of a poorly designed system whereother electrical equipment gives off unwanted high-frequency pulses. There aretwo types of noise: random noise and periodic noise. Random noise (or whitenoise) is a signal added to the original signal in a random fashion and is usually ofa fairly low value. Periodic (or coloured) noise is a signal with some type of regularpattern or shape that is added to the desired signal. Shielding surrounding cablesand equipment reduces the problem of noise. For example, the shielding in acoaxial cable allows data to be transmitted with little distortion.

A signal that is affected by noise needs to be filtered. Filters are used to get ridof noise and get a smooth signal (see Figure 6.12). Just as filters on a water supplyremove dirt and grease, so electrical filters remove unwanted noise from the signal.High-pass and low-pass filters are devices that remove frequencies above or belowa certain value. For example, noise might be added to a high-frequency signal.Thisnoise could be removed by using a high-pass filter that only allows high-frequencysignals to pass. Noise is also reduced by signal conditioning.

211

High-frequencynoise level

(a)

Low-frequencysignal from sensorwith noise added

(b)

Signal fromsensor with noiseremoved by low-pass filter

(c)

Figure 6.12 Filters.

212 Options

Noise can cause errors in the transmission of digital signals. Error checkingtechniques for digital signals were discussed in Chapter 3. Errors in a digital signalmust first be detected and then corrected. Three common methods for errordetection are parity checking, checksum and cyclic redundancy check.

1 What is mass production?

2 Outline some of the benefits of mass production.

3 Describe a trend in mass production.

4 List three types of production used in automated manufacturing systems.

5 What is a continuous system?

6 Outline some of the disadvantages of a batch system.

7 Describe a discrete system.

8 What is an actuator?

9 Briefly describe five different types of actuators.

10 What is the purpose of a DAC?

11 Why is signal conditioning often needed in automated manufacturing systems?

12 Explain the difference between a signal and noise.

13 Describe two techniques that reduce the problem of noise.

LEARNING ACTIVITIES

1 An automated manufacturing system is being designed to produce kitchen tablesfor domestic use. The factory aims to cater for a range of different retailers andspecific requests from its customers. The intended output of the factory is 10 000tables per year.a What information is needed to set up the factory? b One retailer requires 500 identical kitchen tables every year. Describe the

appropriate type of production.

2 A car manufacturer has decided to produce cars that match the exact colourspecifications obtained from its customers. a Outline any advantages for the customer and the manufacturer for this type of

production.b Draw a data flow diagram to represent the movement of data.

3 Most of the items we use each day are mass produced.a List one mass-produced product that you use.b Describe the automated manufacturing system used to produce this product.c What actuators are used to manufacturer this product?

4 Use a graphics program to design a robot arm that is able to pick up small items.On your diagram, show the type and placement of each of the electric motorsused to operate the arm. Indicate the positioning of sensors and the environ-mental data each sensor is designed to detect (for example, the height of the armabove a conveyor belt).

Exercise 6.4


6.5 Issues related to automatedmanufacturing systemsBoth positive and negative impacts arise from the use of automated manufac-turing systems. In this section, we examine some of the issues raised by automatedmanufacturing systems.

Nature of workAutomated manufacturing systemshave involved replace-ment of peopleby an automated system. The long-term effects of automated manu-facturing systems on employment are adebatable issue. People have lost jobsthrough automation, but populationincreases and consumer demand forthe products have minimised theselosses. Many people argue thatdisplaced workers should be retrainedfor other positions.This argument onlysucceeds if the organisation is growingat a rate fast enough to create newpositions.A worker whose job is takenover by a machine undergoes a periodof emotional stress. On the otherhand, the use of automation doescreate more jobs for people withinformation technology skills (seeFigure 6.13).

213

Automated manufacturing systems affect not only the number of workers butalso the nature of work. Automation is directed towards the use of informationtechnology rather than manual labour. It places a greater emphasis on knowledgeand technical skill than on physical work. The types of jobs found in automatedmanu-facturing systems include machine operation and main-tenance, operators,systems analysis and computer pro-gramming. Workers must be technologicallyproficient to perform these jobs.

Organisations in the manufacturing industry are making a greater effort in theirjob design. For example, operators working on a conveyor can vary their pace byworking ahead and then slowing down, and work breaks occur during production.Organisations are also beginning to recognise that people have different job needs.Some people prefer tasks that are repetitive and narrowly skilled. Other peopleare bored by repetitive tasks. These organisations are providing opportunities forjob rotation and educational programs to diversify employees’ experience and toacquaint them with various aspects of the manufacturing process. This will giveeach employee a concept of the total manufacturing task and the importance ofeach employee’s specific function within that task.

Figure 6.13 People programming a robot.

214 Options

Semi-automationSemi-automation occurs when some tasks are performed by humans and some bymachines. Most factories are only partially automated as they get better results byonly automating some of the functions. For example, in the food industry, a personinspects the food as it passes along a conveyor belt. Poor-quality items are removedfrom production. Another example is the use of machinery to pack and wrapheavy boxes of the product while people move the boxes using a fork-lift.

IITT FFaaccttIT FactRobots are increasingly being used for many different tasks, from shearingsheep and washing windows on tall buildings to assembling parts formachines.

Semi-automation provides advantages to an organisation. The manufacturingprocess can be designed to take into account the strengths and weaknesses ofpeople and machines. People’s strengths are their flexibility, commonsense and ingenuity. They are better than machines at visualising, understanding andthinking of new ideas. Machines are better at repetitive tasks and performingcalculations.

Human-centred systemsMachine-centred systems are designed to simplify what the machine must do atthe expense of participants.They assume people will follow confusing proceduresand still work efficiently. If errors occur in a machine-centred system, they areusually blamed on the participant (operator error) rather than on the technology.Machine-centred systems are not always the best systems for people. Automatedmanufacturing systems consist of many machines; however, the systems should behuman centred.

Human-centred systems are those that make participants’ work as effectiveand satisfying as possible. They allow people to do their work without wastingtime and effort dealing with the information technology. Automated manufac-turing systems should be designed in consultation with the participants. It isimportant that attention is given to the work environment and to the needs of theparticipants, as well as to the information technology. An increasing amount ofresearch has been completed on the relationship between people and machines.This has led to the improved design of tools, machines and participants’ workpositions.

Reliability and qualityAutomated manufacturing systems perform manufacturing processes with greatercontrol and consistency of product than a human worker. They also make moreefficient use of materials, and this results in less wastage. Machines can repeat agiven task almost endlessly and with a great degree of accuracy. Automatedmanufacturing systems can perform repetitive tasks, such as automatic painting,spot welding and newspaper printing, with a great degree of reliability andaccuracy. They provide an opportunity to relieve people from repetitive,hazardous, or unpleasant work. The general idea is to free people to do morechallenging and rewarding jobs.


The reliability and quality of an automated manufacturing system aredependent on participants. Appropriate procedures need to be in place to ensureautomated manufacturing systems maintain reliability and quality. It is not onlythe consistency of the product that is a concern. There are many examples wherelack of quality control has caused a serious accident. For example, the Chernobylnuclear-reactor catastrophe in 1987 would have been avoided with betterprocedures to test reliability and quality. Machines that are improperly designedor used kill many Australians each year.

SafetyAutomated manufacturing systems have improved safety in the workplace.Machines are doing dangerous and hazardous jobs, such as spot welding. Mostautomated manufacturing systems include safety-monitoring systems. Sensorsdetect that a safety condition has developed that may be hazardous to theequipment or to people.The safety-monitoring system takes the most appropriateaction to remove or reduce the hazard. This may involve stopping the machineand alerting maintenance personnel, or it may involve a more complex set ofactions to eliminate the safety problem.

On the other hand, unsafe practices and poor machine design can causeaccidents. In dangerous environments, such as near grinding machines, suitableprotective gear should be worn. This would include earmuffs, face masks andprotective clothing made of heavy material. Dangerous machinery should beshielded from being accidentally touched by workers. General safety issues relateto adequate lighting, ventilation and fire safety measures. Organisations arerequired to provide a workplace that conforms to the Occupational Health andSafety Act. This act provides heavy penalties for organisations that do not provideadequate health and safety conditions for their employees.

215

Case study

Uncle Ben’s Pet Food manufactures suchitems as cat food. It is an example of anautomated manufacturing system that usesrobots together with a human controller. Arobot arm examines the boxes of packagedfood going past on the conveyor belt.When the boxes pass, the robot will inspecteach to see if it is defective in some way.The defect might be the colour of thewrapping paper, incorrect alignment of thelabels, incorrect labels, or holes and tearson the side of the box. The robot has itsgripper over the conveyor belt as the boxespass beneath its camera. When a defectivebox passes the camera, the robot will gripthe box and then move its arm over awaste bin where it will let the box fall intothe bin. The arm will then return to itsoriginal position waiting for the nextdefective box to be selected. It will repeat

this action over and over again.Uncle Ben’s Pet Food factory is a con-

tinuous production system. Food is manu-factured 24 hours a day. People are used tocontrol the moving conveyor belts and fixany breakdowns. When they become tired,there is a greater risk of accidents. Forexample, the operator might get carelessand lean too far over the moving belt andget caught. Uncle Ben’s Pet Food factorywas designed to provide a safe workingenvironment. For example, the movementsof the robot arm were restricted to ensurethe arm does not move too far away fromthe conveyor belt. This is important as itreduces the risk that a worker will be hit by the arm. All moving parts have pro-tective covers, and special ‘stop’ buttonsare within reach of the worker to allow foremergency shutdowns.

Uncle Ben’s Pet Food

216 Options

1 Describe the effect of automated manufacturing systems on employment.

2 How are automated manufacturing systems affecting the nature of work?

3 Describe some of the ways the manufacturing industry is designing jobs.

4 What is semi-automation?

5 Describe the advantages of semi-automation.

6 Outline some ways of designing human-centred manufacturing systems.

7 List some of the repetitive tasks performed by automated manufacturing systems.

8 Why are reliability and quality important in an automated manufacturing system?

9 What is safety monitoring?

10 Describe some of the ways manufacturing industries can improve safety.

11 The following questions relate to the Uncle Ben’s Pet Food case study:a Describe the automated manufacturing system.b List some of the information technology used in this system.c Outline some of the safety issues in this system.

LEARNING ACTIVITIES

1 The introduction of information technology into the manufacturing industry haschanged the nature of work. Choose one manufacturing industry and comparethe tasks performed by the employees before and after the introduction ofinformation technology. What old skills have been lost and what new skills havebeen developed in the process of automation?

2 Explain the meaning of the term ‘quality control’ when applied to an automatedmanufacturing system. Illustrate your answer with an example.

3 What are some of the safety issues that might affect you at school? Do any ofthese issues apply to the workers in an automated manufacturing system?

4 Should workers be trained in first aid at a factory? Who do you think should payfor this training? Who is responsible for worker safety at a factory?

5 Automated manufacturing systems are having a positive and negative impact onour society. Briefly describe some of the changes to our society caused byautomated manufacturing systems. What do you think is the greatest concernwith automated manufacturing systems? Give a reason for your answer.

Exercise 6.5

Chapter review

Automated manufacturing systems 217

PART A


1 The process of producing a product thatmeets a specific need is:A automationB manufacturingC automated manufacturing systemD actuator

2 Direct users of an automated manufac-turing system do not:A interact with the information tech-

nologyB perform the actual work on the

productC include supervisors who oversee the

operationD control the manufacturing system

3 The use of information technology todesign and analyse a product is called:A CADB design specificationsC CIMD IT design

4 A form of programmable automationin which numbers control a machine is:A binary codeB automatic codeC NCD controller

5 A thermistor is a temperature sensorthat:A measures the temperature using two

different metals in electrical contactB uses a semiconductor device to

measure temperatureC measures temperature using a

metallic conductorD uses a liquid or gas to measure

temperature

6 Which of the following terms is notrelated to light sensors:A potentiometerB photodiodeC CCDD barcode reader

7 A type of damping that occurs if thechange is too fast and it overshoots thedesired level is:A fastdampingB underdampingC overdampingD critical damping

8 A batch system is a type of productionthat:A is capable of operating 24 hours

per day for weeks or months withoutstopping

B performs a single task in a small timeinterval

C produces output usually measured byvolume or weight

D produces a specific quantity of aproduct

9 An actuator that consists of a coil of wirearound a movable magnet is called a:A solenoidB stepper motorC relayD magnetised coil

10 A major problem with mass productionis the:A standardisation of the partsB balance between human effort and

machineryC maximisation of the outputD inflexibility of the system



Statements

1 The use of information technology todesign and analyse a product or object.

2 A form of programmable automationin which numbers control a machine.

3 The physical form in which data istransmitted, such as pulses of electricityin a wire.

4 A production system that performs asingle task in a small time interval.

5 A display device that performs amechanical action under the control ofa signal from a controller.

6 The process of producing a product thatmeets a specific need.

7 An information system involved in pro-duction by inventory tracking, record-keeping, production scheduling andactual production.

8 The use of automatic control for thestorage of products.

9 A system capable of operating 24 hoursper day for weeks or months withoutstopping.

10 The specialised information technologytools that automate the entire manu-facturing process.

11 An input device that measures datafrom the environment.

12 The process that modifies the signal tothe output device based on the inputsignal.

13 A series of workstations connected by atransfer system that moves partsbetween each workstation.

14 The manufacture of products in largequantities by standardised mechanicalprocesses.

15 Unwanted data or interference thatreduces the quality of a signal.

16 The application of automatic control toindustrial processes.

List of terms

a actuator

b assembly line production

c automated manufacturing system

d automated warehouse

e automation

f CAD

g CAM

h continuous system

i damping

j discrete system

k manufacturing

l mass production

m noise

n NC

o sensor

p signal

PART C


1 What are the characteristics of an auto-mated manufacturing system?

2 Explain the difference between the fol-lowing terms:a a continuous and a batch systemb an actuator and a sensorc CAD and CAM.

3 Outline three reasons for automation.

4 Describe assembly line production.

5 Briefly describe five different types ofsensors.

6 What are the three types of damping?Briefly explain the differences.

7 Outline one method of removing noisefrom a signal.

8 Identify a social or ethical issue involvedin automated manufacturing systems.Identify both the positive and negativeaspects of the issue.

218 Options

77MMUULLTTIIMMEEDDIIAASSYYSSTTEEMMSS

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Outcomes

This chapter examines the characteristics ofmultimedia systems, including the different types of media used in these systems. Itinvestigates the software and hardware used toprepare and display multimedia. The informationprocesses of a multimedia system and the social and ethical issues related to multimediasystems are presented.

Overview

220 Options

7.1 Characteristics of multimediasystemsA multimedia system is an information system that combines different types ofmedia. It uses at least three media types, such as text, images, animation, audioand video. Multimedia systems have the potential to provide a better experiencethan any other information medium. They can combine the best of television,film, graphics, animation, books, magazines and radio. The result of a multimediasystem is called a multimedia product or a multimedia presentation. Multimediais created and displayed using a range of software, such as authoring software andpresentation software.

Types of media The types of media used in a multimedia product include text, numbers,hypertext, audio, images, animations and video.

Text, hypertext and numbersText refers to letters, numbers and other characters whose meaning and format isnot specified. It has no meaning until a person reads and interprets it. Text in amultimedia product is written using a word processor.The first basic concern withtext is how much information should be presented. It is recommended that eachscreen should only relate to one task or piece of information. The screen shouldnot be overloaded with text.

Hypertext allows the user to navigate through a multimedia product. It is asystem that allows documents to be cross-linked in such a way that the user canmove from one document to another by clicking on a link. A hyperlink (link orhotword) is the highlighted item (usually an underlined word or a graphic) thatallows the electronic connection (see Figure 7.1). The author of the hypertextmust specify the location of the information accessed by each link. In a multi-media product, the link may be to text, an image, audio, animation or video.Whenyou click on a link, you move from one document to another even if they aredifferent media types. Hypertext provides the interactivity in a multimediaproduct. The most well-known application of hypertext is the Web.

Numbers refer to predefined characters, usually numerals, whose meaning andformat are specified. Calculations are often performed on this data type. For

Figure 7.1 A hypertext link.

Multimedia systems

example, the purchase amount is a number with a predefined dollar format.Numbers may take different forms but are sometimes linked to some type of chart.

AudioAudio is sound that has been digitised.The meaning of audio data is determined bylistening to and interpreting the sounds. Audio has become an essential part ofmost multimedia products. It is used to explain concepts, reinforce selections andprovide special effects. Sounds may be available in digitised form or may have to beconverted before use. Audio files tend to be large and may be very slow to load instandard WAV format. The development of the MP3 format for audio has greatlyimproved quality and decreased both transmission time and storage requirements.

ImagesImages are pictures, such as drawings, paintings or photographs.The meaning of animage is determined by looking at the image and interpreting it. Images are usedto create interest and provide information. All images on the screen are made upof tiny dots called pixels. A pixel, or picture element, is the smallest part of thescreen that can be controlled by the computer. The total number of pixels on thescreen is called its resolution. Images are either bit-mapped graphics or vectorgraphics.

Bit-mapped graphics treat each pixel on the screen individually and representthis by bits in memory. They produce good quality images where shading anddetail are needed. However, when transformed (resized or stretched), bit-mappedgraphics become ragged and suffer loss of resolution. Enlarging each pixel in a bit-mapped graphic creates a staircase pattern called aliasing. Bit-mapped imagesrequire large amounts of storage. They are often stored in compressed formats,such as GIF and JPEG.

Vector graphics are made up of objects, such as a straight line, a curve, or ashape. Each object is defined by its characteristics, such as position, line width, andpattern. These characteristics are stored as mathematical expressions anddisplayed on the screen as pixels. Some common formats for vector graphicsinclude CGM, EPS and WMF.

221

IITT FFaaccttIT FactThe aspect ratio is the relationship between the vertical and horizontal sizeof an image. In normal television, the aspect ratio is 3:4, and in digitaltelevision the aspect ratio is 9:16.

AnimationAnimation is the movement of a graphic. It is the result of a series of still images,or frames, presented in rapid succession. Each frame used in an animationsequence is called a cell (or cel). The term ‘cell’ derives from the traditionalcartoon frames that were hand-drawn on separate sheets of celluloid. Animationscan present information more effectively than text or an image. For example, ananimation that shows the movement of blood throughout the body is moreeffective than a still image. Animations are usually started by entering a page orclicking a button. Animated GIF and QuickTime are two common formats foranimation.

222 Options

VideoVideo combines pictures and sounds displayed overtime. It is important to note the difference betweenvideo and animation. Video starts with a continuousevent and breaks it up into discrete frames. Animationstarts with independent pictures and puts themtogether to form the illusion of movement. MPEG is afamily of formats for compressed video that has becomea standard for many applications. QuickTime is a videoand animation format developed by Apple Computer. Itis built into the Macintosh operating system and usedwith most Macintosh applications. Apple has alsoproduced a QuickTime version for Windows. Video canbe displayed in a multimedia product by inserting avideo player (see Figure 7.2).

Print and multimediaThe major differences between print and multimedia versions of similar contentare the mode of display and interactivity.

Mode of displayPrinted information is displayed using a printer or plotter. In contrast, amultimedia product is displayed using a screen and speakers:• A screen is a display surface that provides immediate feedback about what the

computer is doing. It can display text, image, animation and the visual portionof video data. Every screen is capable of displaying more than one resolution.The resolution and size of the screen affect the quality of the multimediaproduct. Multimedia products are often displayed on an information kiosk. Itallows people to use a touch screen and select information about anorganisation or service.

• A speaker is a device used to produce sounds.A small speaker is usually locatedin most personal computers inside the system unit. However, high-qualitystereo speakers are often connected to the computer, using a port and a soundcard, or are built into the sides of the monitor.

InteractivityA major difference between print and multimedia is interactivity. Interactivityallows the user to choose the sequence and content of information. A multimediaproduct is often judged on the quantity of its interactivity. The Internet is anexample of an interactive environment. The expression ‘surfing the Net’ or‘browsing’ refers to the experience of jumping from one page to another usinginteractivity. Interactive multimedia accepts input from a mouse, touch screen orkeyboard and performs some action. Hypertext and hypermedia are used tonavigate through a multimedia product. The product may link audio, image,animation, video or another screen. Print provides a limited form of interactivity.In books, it is possible to choose the sequence and content of the information byreferring to the contents and the index.

Figure 7.2 A video playerin a multimedia product.

Multimedia systems

Hardware demands by multimedia systemsThe developments in information technology have allowed people to createmultimedia products that were once only developed by film professionals. Thehardware of a multimedia system places limits on the quality and size of themultimedia product that can be produced or displayed. For this reason, amultimedia system makes use of the latest technology, such as a fast processor,large primary storage, high-resolution screen, quality speakers, and the latest indisk drives.

Image storageImages place extra demands on the multimedia system including storage. Thecurrent image being displayed is stored in a section of memory called the framebuffer. When selecting images to include in a multimedia product, it is importantto consider the format of the image and the resolution of the presentation device.Large high-resolution images may affect the performance of the multimediaproduct. An image with high resolution will require more memory than an imagewith low resolution. The storage requirements of an image are dependent on thenumber, size, tone and colour of each pixel. The relationship between the imageon the screen and the bits in memory is called bit mapping, or memory mapping.It is dependent on the bit depth.

Bit depth (or colour depth or pixel depth) for images is the number of bits perpixel. One or more bits must be stored for each pixel on the screen. At thesimplest level, one pixel can represent one bit, where a 0 bit means the pixel is offand a 1 bit means the pixel is on.

Example: What is the file size in kilobytes of a black-and-white image with aresolution of 640 by 400 pixels?

File size = Horizontal × Vertical × Bit depth8 × 1024 bits (= 1 Kb)

= 640 × 400 × 18 × 1024

= 31.25 Kb

223

Bit depth Number of colours Relationship(bits per pixel) or tones

1 2 21 = 2

2 4 22 = 4

3 8 23 = 8

4 16 24 = 16

6 64 26 = 64

8 256 28 = 256

16 65 536 216 = 65 536

24 16 777 216 224 = 16 777 216

32 4 294 967 296 232 = 4 294 967 296

Table 7.1 Relationship between bit depth and tones or colours.

224 Options

Colour graphics and graphics with tones (or grey scale) increase the number ofbits per pixel and require more storage. Colour graphics are obtained from anRGB (red-green-blue) screen that uses a combination of red, green and bluecolours. The minimum number of colours is eight: red only; green only; blue only;red and green (yellow); red and blue (magenta); blue and green (cyan); red, greenand blue (white); and no colour (black). For example, as shown in Table 7.1, a bitdepth of 8 allows a graphic to contain 256 colours, or 64 colours each with 4 tones(64 × 4 = 256), or 32 colours each with 8 tones (32 × 8 = 256). Photo realisticimages require at least 24-bit colour.

Example: What is the file size in kilobytes of a 256-colour image with aresolution of 1024 by 768 pixels?

File size = Horizontal × Vertical × Bit depth8 × 1024

= 1024 × 768 x 88 × 1024

= 768 Kb

Audio storageSound travels through the air in waves with a particular volume and pitch. Asound wave is analog data. Analog data is represented by continuous variablequantities while digital data is represented in the form of digits or numbers.Computers are digital.Audio is sound that has been digitised. It is created using ananalog-to-digital converter (ADC) and reversed by a digital-to-analog converter(DAC). The ADC and DAC are built into the computer’s motherboard or areadded using a sound card.

The method used by the ADC to digitise a sound wave is called sampling (seeFigure 7.3). Sampling has three important characteristics: the sampling rate, thesampling size and whether the sound is mono or stereo:• Sampling rate is the number of times a sample (slice) is taken from the sound

wave. During a sample, the amplitude of the wave (volume) is measured andconverted to a number. Two common sampling rates are 44.1 kHz (44 100samples per second) and 22.05 kHz (22 050 samples per second). The higherthe sampling rate, the better the sound (see Table 7.2).

• Sample size (or bit resolution) is the number of bits per sample. The mostcommon sampling sizes are 8-bit sound and 16-bit sound. Better-quality soundis recorded using 16 bits; however, for most voice uses, 8-bit sound is sufficient.CD-quality stereo sound requires 16 bits.

Sampling rate Best uses11 kHz Recommended for speech and short segments of music

22 kHz Better music playback

32 kHz Broadcast audio standard

44 kHz CD-quality audio playback

48 kHz Digital audio tape (DAT) playback

Table 7.2 Sampling rates and their uses.

Multimedia systems

• Mono uses one channel of sound, and stereo uses two channels (left and right).Stereo sound is regarded as the better sound.An audio file size is calculated by multiplying the sample rate, the sample size

and the time in seconds. If the file is in stereo, then the result of the previouscalculation is multiplied by 2.

Example: Calculate the file size of a CD-quality audio that uses a sample rateof 44.1 kHz with a 16-bit sample size and a track that lasts for three minutes instereo:

File size = (Sample rate × Sample size × time) × 2

= 44 100 × 16 × 180 × 2 bits

= 254 016 000 bits

= 31 752 000 bytes (1 byte = 8 bits)

= 30.28 Mb (1 Mb = 1 048 576 bytes)

The large file size of CD-quality audio has been a problem. MP3 format is acompressed format that reduces this problem. It filters out superfluous infor-mation from the original audio source. This results in smaller audio files with noapparent reduction in quality. In general, one minute of music equals 1 Mb in anMP3 file. This can vary depending on the type of compression chosen and thesoftware used (see Table 7.3).

225

Digital audio system

Audio input

Audio output

Sampling

A/Dconversion

Reproducedsignal

D/Aconversion

Disk

+3+2+10

–1 –2 –3

0 +2 +3 +2 –1 –3 –2 0100 110 111 110 011 001 010 100

+3+2+10

–1 –2 –3

Figure 7.3 Sound wave and its digitised form.

226 Options

Video processingVideo can be an excellent medium to explain concepts; however, it places extrademands on the multimedia system.A decision to use video is often made in termsof providing exciting additional elements and ensuring the multimedia productwill function effectively. A video camera is used to create a video clip in analog ordigital form.Analog signals need to be converted into digital using a video capturecard. Digital video production software is used to edit the video into a multimediaproduct. Editing may involve adding text, audio or images to the video clip.Videofiles are usually very large, and this factor must be taken into account beforeincluding them in a multimedia product.

To satisfactorily display video or animations, we need to consider the speed atwhich the image can be shown. The speed of a video or animation is called theframe rate. It is measured by the frames per second (fps). The higher the framerate, the smoother the video or animation (see Table 7.4). Full-screen video oranimation requires a fast processor and a lot of random access memory.

Audio track time WAV MP34.11 minutes 42.4 Mb 3.5 Mb

3.33 minutes 36 Mb 3 Mb

8.16 minutes 83.5 Mb 6.95 Mb

Table 7.3 File sizes for WAV and MP3 files.

Frames per second Examples30 Screen refresh rate of monitors

25 Video speed for the PAL system

24 Film speed for motion pictures

12 Cartoon animation speed

8 Minimum speed for the illusion of motion

Table 7.4 Comparison of frame rates.

Large videos and animations can also require large storage facilities. Forexample, calculate the file size in kilobytes of a 90-minute movie at 24 fps. Eachframe is 2048 by 872 pixels with 32 bits for each pixel:

Number of frames = (Frame rate x time in seconds) = 24 × 90 × 60= 129 600 frames

File size for each frame = Horizontal × Vertical × Bit depth8 × 1024

= 2048 × 872 × 328 × 1024

= 6976 Kb

File size for movie = 129 600 × 6976

= 904 089 600 Kb

= 862.207 03 Gb (1 Gb = 1 048 576 Kb)

Multimedia systems

Animation processingAnimation creation is affected by the size of the image and the speed of themovement. It is frequently set at 30 frames per second, or 9000 frames for a five-minute animation (30 × 60 × 5). This creates a smooth illusion of movement.However, drawing 9000 images is a huge task. A computer with animationsoftware makes this task much easier. Animation is created using path-based andcell-based animation.

Cell-based animation (or cel animation) involves drawing and displayingindividual frames or cells. Each frame is stored separately and loaded into agraphics page of primary memory. It is the traditional method of animation. Theanimation works by displaying the first frame from a graphics page while creatingthe second frame in another graphics page. The second frame is slightly differentfrom the first frame depending on the items to be animated. The second frame isthen displayed, and the third frame is created in the graphics page of the firstframe. Animation occurs by alternating the display of graphics pages.This method of animation requires a very powerful computer to achieve 30 frames per second. For example, a high-resolution colour graphic containing500 000 pixels would require calculations for 15 million (500 000 × 30) pixels inone second. A fast processor and a large fast-access storage device are required toensure that the animation flows at the appropriate speed. For this reason, path-basedanimation is preferred.

Path-based animation involves displaying the movement of objects onto a fixedbackground in a particular sequence or path. The pixels in the background do notchange, only those for the moving object.This saves memory and processing time.Animation is achieved by drawing the object, wiping it, and then drawing theobject in a new position. This process is made easier because animation softwarecan generate the intermediate frames between two objects.This is called tweening(short for in-betweening). It is a key process in computer animation.

Morphing and warping are animation techniques that create special effects.Morphing is the smooth change between two different images. It transforms theshape, size, dimension, and colour of one image into those of another. Morphingresults in one image merging into another (see Figure 7.4). For example, a

227

Figure 7.4 Morphing.

228 Options

Warping involves transforming or distorting a portion of the image. It dividesthe image into objects that can be manipulated (see Figure 7.5). For example, asad face could be given a smile with the remainder of the face staying the same.Warping involves one image while morphing requires two images.

Figure 7.5 Warping.

People in multimedia systemsMultimedia products are usually designed by a group of people who have anexpertise in a particular field. Each person works on a different part of the project.There are people who are responsible for the system design, content and each ofthe media types, as well as people with information technology skills. Multimediaproducts require careful planning. People involved in multimedia systems include:• Content providers are people who provide the material for the multimedia

product. This may include text, graphics sketches or final drawings, videofootage and audio tracks. Generally these people are skilled in their field with-out necessarily having any technical skills in the software or hardware areas.

• The system designer plans and organises the hardware and software requiredfor the presentation. He or she may also act as the project manager or providetechnical support.

• The project manager organises the scheduling of various components of theproduct, provides overall supervision of the components and ensures that allcomponents are delivered on time.

• The technical staff includes a variety of artists and technicians who edit thegraphic and video material, text and all other material into appropriate formatsfor the final document. It also includes layout and design personnel who workto develop an overall theme and look of the product. These people may alsoinclude the content providers, or they may be a totally separate group.People may be multi-skilled and work in different aspects of the multimedia

product at the direction of the project manager. The development of anypresentation involves a great deal of planning. This leads into a more detailedproject plan.

Multimedia systems 229

IITT FFaaccttIT FactA ‘Webmaster’ is responsible for the coordination of all tasks to keep a Website active, secure and functional. The daily operation of a Web site iscompleted by a person called a ‘gatekeeper’.

1 What is a multimedia system?2 List seven different types of media used in multimedia products.3 Explain the difference between the media types of text and number.4 Describe a hyperlink or hotword.5 Why is audio an essential part of most multimedia products?6 What are the advantages and disadvantages of a bit-mapped graphic?7 Explain the differences between animation and video.8 What is interactivity?9 Where are current images stored?

10 Explain the difference between the sampling rate and the sampling size.11 What is the frame rate? How is it measured?12 Explain the difference between cell-based animation and path-based animation.13 Why is tweening a key process in computer animation?14 Describe morphing.15 Describe the roles of the people involved in producing a multimedia presentation.

LEARNING ACTIVITIES

1 Calculate the size of the following graphics (answer in Kb to the nearest wholenumber):a A black-and-white graphic with a resolution of 640 by 480 and 2 tonesb A colour graphic with a resolution of 1024 by 768 and 64 coloursc A colour graphic with a resolution of 1600 by 1200 and 1024 colours each with

64 tonesd An 8-bit colour graphic with a resolution of 1280 by 1024e A 32-bit colour graphic with a resolution of 1152 by 864.

2 Calculate the size of the following audio files (answer in Mb, correct to twodecimal places):a Sampling rate of 22.05 kHz with an 8-bit sound for two minutes in stereob Sampling rate of 44.1 kHz with a 16-bit sound for three minutes in stereoc Sampling rate of 22.05 kHz with a 16-bit sound for one minute in monod Sampling rate of 11 kHz with an 8-bit sound for four minutes in monoe Sampling rate of 44.1 kHz with a 16-bit sound for ten minutes in stereo.

3 Calculate the size of the following video files (answer in Gb, correct to twodecimal places):a Frame rate of 25 fps, 120 minutes, frame resolution of 1024 by 768 pixels with

16 bits per pixelb Frame rate of 30 fps, 75 minutes, frames resolution of 1600 by 1200 pixels with

32 bits per pixel

Exercise 7.1

230 Options

7.2 Examples of multimedia systemsMultimedia has developed into a major industry. It is being applied in most areasof our society, and recent advances in technology are influencing furthermultimedia development.

Major areas of multimedia useThere are four major areas of multimedia use: education and training, leisure andentertainment, information, and virtual reality and simulations.

Education and trainingMultimedia systems are very effective at helping people to learn. A good multi-media product that uses different media types can maintain the user’s interest.The interactive nature of multimedia allows the user to control the learning. Itaddresses each user’s particular needs. Multimedia systems also allow training tobe carried out at convenient times and are developed to cater for a wide range ofabilities. They are a cost-effective method of education and training.

Computer-based training (CBT) is a type of multimedia product used foreducation and training. A person uses CBT at his or her own pace. Information ispresented using different types of media, and the user has the opportunity to reviewmisunderstood concepts. CBT products are designed by experts in their fields anddesigned to cater for different rates of learning.The ‘Typing Tutor’ is a simple exampleof CBT that is designed to improve keyboard skills. Interactivity in CBT is the basisfor an individual to progress through the system. CBT usually contains some form ofassessment to determine whether an individual is ready for the next level.

Leisure and entertainmentMultimedia systems designed for leisure and entertainment are generally classifiedas computer games. Computer games provide a high level of interactivity. Theresponses of the user determine the game being played.The sequence of actions maybe limited by the game designer or may have a large range of possibilities. Gamestend to be time restricted and have complex animation. The level and amount oftext is limited. Depending on the type of game, the navigation may be deliberatelyhidden until the user reaches a certain level. Computer games feature high

4 The resolution of a screen is set at 640 by 480 pixels. What is the size of the framebuffer for (answer in Mb, correct to two decimal places):a 8-bit colour images?b 32-bit colour images?

5 A shopping centre is creating a multimedia display for an information kiosk. Whattypes of media could be used in the display? Give an example of the informationto be displayed by each type of media.

6 Multimedia productions, such as television, are being displayed on the Internet.Outline some of the benefits for users and owners of Internet television overtraditional television.

7 Pauline has scanned a photographic image of her dog. She wants to display thephotograph using 24-bit colour. Is 24-bit colour a suitable bit depth? What fileformat would be suitable to save this photograph onto a hard disk with limitedfree space? Explain your answer.


resolution images, audio, and animation or video. They often use some form ofalternative to the keyboard, such as a joystick, for input. Developments intechnology have resulted in computer games that are more realistic (see Figure 7.6).

InformationMultimedia systems provide users with an easy way to display information.The usercontrols when, how and what information will be displayed. The interactive natureof multimedia allows the user to search using related keywords to find specificinformation (see Figure 7.7). This is a distinct advantage over printed forms of thesame material. A multimedia encyclopaedia is a good example of a multimediasystem used to obtain information. It displays information using text, colour, audio,and video or animation. This makes it easier for people to understand information.

Figure 7.6 Characters from the computer game Carmaggedon.

Figure 7.7 The Encyclopaedia Britannica Web site.

232 Options

Information kiosks allow people to use a touchscreen and select information about an organisation orservice (see Figure 7.8). The information displayeddepends on the selections of the user. Informationkiosks commonly provide information about items, thelocation of items or a map to a particular product orservice. They use large navigation buttons with fewoptions. Information kiosks can also be used to provideinformation to the organisation. The selections madeby the user are a source of information about the levelof interest in a product or service.

Virtual reality and simulationsMultimedia systems are used for virtual reality andsimulations. Virtual reality (VR) is the use of computermodelling and simulation to enable a person to interactwith an artificial environment.VR immerses the user inan environment that simulates reality through the use

of interactive devices, such as goggles, head-up displays, gloves, or body suits (seeFigure 7.9). In a common VR application, the user wears a helmet with a screen foreach eye to view animated images of a simulated environment. Motion sensors thatpick up the user’s movements and adjust the view on the screens create the illusionof reality. Data-gloves equipped with force-feedback devices provide the sensationof touch. The user picks up and manipulates objects that he sees in the virtualenvironment. VR is highly interactive.

Figure 7.8 Information kiosk.

Figure 7.9 Virtual reality mask.


Flight simulators are used to train pilots.The external effects, such as changingweather conditions, require high-resolution images and the ability to controldifferent aspects of the system. Different scenarios are carefully modelled, and thereactions of the plane are made as realistic as possible. Flight simulators tend torequire a lot of physical room as they involve complex hydraulic systems. Thismakes them expensive. However, ‘crashing’ a flight simulator is cheaper thancrashing a real plane.

IITT FFaaccttIT FactSimnet (simulator network) was a network of workstations that enabledmilitary personnel to practice combat operations on interactive, real-timetraining systems. It was used to prepare U.S. troops for the Persian Gulf Warin 1991.

Advances in technologyAdvances in technology are influencing multimedia development. For example,increases in processing speed have allowed video and animation to move atrealistic speeds.The improvements in storage capacity have allowed better-qualityimages to be a part of the multimedia production. Dramatic progress in com-munication technology has allowed multimedia to be displayed on the Internet. Itis now possible to access audio and video over the Internet in real time. Threesignificant advances in technology that have influenced multimedia are the WorldWide Web, CD-ROM speed and DVD.

World Wide WebThe World Wide Web (WWW or Web) is an Internet network that allows peopleat one computer to collect information stored on another. People connect to othercomputers to look at Web sites. A Web site is group of documents that presentinformation on a particular topic. Each single document is called a Web page.These Web pages are stored on powerful computers called servers. Each serverstores thousands of Web pages from different Web sites. To view a particular Website, the computer connects to the server and receives the Web pages.

The Web is an interactive environment. A hyperlink instantly connects toanother web page with a click of the mouse button. The expression ‘surfing theNet’ or ‘browsing’ refers to the experience of jumping from one page to anotherusing hyperlinks. A hyperlink takes the user to another Web site, or another pagewithin the Web site, or even another location on the same Web page.

Development on the Web has exploded. The increased power of personalcomputers and increased speed of access have made the Web a valuable multi-media tool. Organisations and individuals are creating Web sites that containmultimedia material to present information (see Figure 7.10). This information isdisplayed around the world at a reasonable cost.

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CD-ROM speedCD-ROM (compact disc with readonly memory) disks are 12 centi-metres wide and capable of storing650 Mb. However, the data is readonly and cannot be changed. CD-ROMs are convenient for storingdata that remains constant, such asmultimedia applications. A CD-ROM drive is needed to read data(see Figure 7.11). The speed ofCD-ROM drives has steadily in-creased, resulting in faster retrievalof data. These improvements havemade multimedia products ap-proach a more realistic level.

DVDDVD (digital versatile disk) is a disk format that can store large amounts of data. Itis an optical disk storage medium that may replace audio CD, CD-ROM, videotapeand video game cartridges. DVD has the ability to produce studio-quality video andaudio. DVDs can store full-length movies. There is DVD Video and DVD-ROM.

DVD Video holds video and is played in a DVD player connected to thetelevision. Data is compressed (lossy) in MPEG-2 format. However, there is nonoticeable effect on the quality of the video. DVD Video is formatted to play oneither of two mutually incompatible television systems: 525/60 (NTSC) or625/50 (PAL/SECAM). Video equipment in Australia must conform to the PALsystem, whereas the USA uses the NTSC system.

Figure 7.10 Web site containing multimedia.

Figure 7.11 CD-ROM drive.


A DVD-ROM is the same size as a CD-ROM but provides storage of 4.7 Gbto 17 Gb. DVD-ROM drives can play CD-ROM and audio CD, and most DVD-ROM drives will play DVD Videos.

One of the major advantages of a DVD is that text, image, video and audio havethe same file structure. This file structure is called UDF (Universal Disc Format).This overcomes problems of incompatibility with multimedia applications.

IITT FFaaccttIT FactPolymedia is an advanced and highly sophisticated multimedia system usedin defence, industry and medicine. It uses supercomputers to provide real-time animation and simulation.

Multimedia designDesigning multimedia products involves more than simply using the authoringsoftware. Good design is critical to the success of a multimedia product. (SeeFigure 7.12.)

Design principlesThe different media types must be combined into one effective multimediaproduct. The design of each screen should be based on the three basic designprinciples:• Consistent. Layout, format and style should be the same throughout the

multimedia product unless different media types demand a change. Readabilityis improved when similar items are grouped. Grouping is achieved by spacing,using colour for the text, changing the backgrounds, or using borders.

• Navigation. People need to understand the structure of the multimediaproduct and easily proceed to the desired information. The time the multi-media product takes to respond to a particular action is important. Peoplebecome frustrated if they are waiting more than a few seconds for the nextscreen or a video clip to load.

Figure 7.12 Web site promoting good design.

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• Simple. Do not use too many design elements as it often confuses the user.Theoveruse of colour, sound and animations can be distracting.

MediaText depends on the purpose, the intended audience and the method of displayingthe multimedia product. There are some generally accepted design principles toformat text:• Characters. Avoid using too many fonts. San serif typefaces can be clearer than

serif typefaces on the screen. Care should be taken when using font styles suchas bold and italic. Long lines of text are difficult to read.A multimedia productoften uses a larger type size, such as 20 point, than a word processing docu-ment would. Headings can be written in serif or san serif typefaces. Differentsize headings reflect their importance.

• Screen layout. Appropriate conventions exist for column width, alignment, linespacing, character spacing, indentation, hyphenation, and kerning. Bullets andnumbering are a common way to organise text in a multimedia product.

• Text colour. Colour contributes to the style and theme of a multimediaproduct and draws attention to the text. Some colours should not be usedtogether as they produce poor contrast and reduce readability (for example,blue text on a red background). Too many colours can be distracting andreduce readability. A colour scheme is used to ensure the colours result in aprofessional-looking multimedia product.

Images and animations are used to create interest and provide information.However, they place extra demands on the multimedia system. The position andsize of an image or animation is dependent on its importance and balance withthe other design elements. They can support or weaken a multimedia product.If too many images are used, they lose their impact.The same goes for animations.Animations should be used sparingly, such as to introduce a new section withinthe multimedia product. Images and animations are edited and adjusted to suitthe screen resolutions. The resolution of an image is dependent on the screen andthe number of colours that can be displayed. The intention of an image must beeasily understood. For example, an image might guide the user to another sectionof a multimedia product. Titling is the placement of a caption to accompany animage or graphic element.

Audio and video are also used to create interest and provide information. Anoccasional burst of sound for special effects will focus the audience on themultimedia. However, the frequent use of sound effects can draw attention awayfrom the main information. Audio and video can be excellent media to explainconcepts; however, they place extra demands on the multimedia system. Audioand video files are usually very large, and this factor must be taken into accountbefore including them in the multimedia product.


1 Why are multimedia products effective at helping people to learn?

2 Why do computer games have a high level of interactivity?

3 Outline a distinct advantage of multimedia over printed forms of the samematerial.

4 What is commonly provided in information kiosks?

5 What is virtual reality?

6 List some of the interactive devices used in VR.

7 How does a flight simulator train pilots?

8 List three significant advances in technology that have influenced multimedia.

9 How is the Web an interactive environment?

10 What factors have made the Web a valuable multimedia tool?

11 Why has the speed of the CD-ROM drive been important in the development ofmultimedia?

12 What is DVD?

13 What compressed file format does DVD Video use?

14 Describe a DVD-ROM.

15 Why is UDF an important file structure?

16 Describe three basic design principles for a multimedia product.

17 What are some of the design principles for text colour?

18 What is titling?

19 When should audio and video be used in a multimedia product?

LEARNING ACTIVITIES

1 Multimedia systems perform information processes requiring participants, data/information and information technology. Clearly identify the participants, data/information, and information technology in these major areas of multimedia use:a education and trainingb leisure and entertainmentc informationd virtual reality and simulations.

2 Use a multimedia encyclopaedia and a print encyclopaedia to research the sametopic:a Comment on the similarities and differences between the two encyclopaedias.b Describe the type of media used in the multimedia encyclopaedia.c What navigation methods were used in the multimedia encyclopaedia?d Is it possible to improve on the navigation methods in the multimedia

encyclopaedia? How?

3 Review at least five Web sites that contain different types of media. Comment oneach Web site in terms of design; ease of use; how the media affects the siteoperation; and the relevance of audio, video and image files.

4 An interactive multimedia product about your local community is to be created:a What type of media could be used in the display? Give examples of each type.b How could the product be interactive?

Exercise 7.2

238 Options

7.3 Displaying in multimediasystemsMany different tools are used for displaying a multimedia system. Multimediasystems depend on both hardware and software to create and display differenttypes of media.

HardwareThe hardware for creating and displaying multimedia includes screens, projectiondevices, speakers, CD-ROM, video and head-up displays.

ScreensA screen is a display surface that provides immediate feedback about what thecomputer is doing. It can display text, image, animation and video data. The mostcommon type of screen is a monitor. It uses CRT (cathode ray tube) technology.

CRT displays produce images by firing a stream of electrons onto the inside ofthe screen, which is coated with tiny dots or pixels made of phosphor. Monochromemonitors use one stream, and colour monitors use three streams to strike red, greenand blue phosphor (see Figure 7.13). When the stream of electrons hits the pixel,the phosphor glows to produce the image. The process by which the colour of apixel changes gradually from its original colour to a new colour is called a cross fade.The total intensity of the pixel usually remains constant during this process.

c Describe the design features that could be used in the product.d Design a home screen for this product.

5 A multimedia Web site is to be created to describe the important developments incomputer technology over the last fifty years:a What type of media could be used in the display? Give an example.b How could the product be interactive?c Describe the design features that could be used in the product.d Design a home screen for this product.

Three electron guns are locatedat the back of the monitor’scathode ray tube (CRT).Each electronic gun shootsout a stream of electrons,one stream for each of the threeprimary colours: red, blueand green.

The magnetic deflectionyoke bends the path ofthe electron streams.

The beams pass throughholes in a metal platecalled a shadow mask,which aligns them withtheir targets on theinside of the CRT’sscreen.

The electrons strike thephosphors coating theinside of the screen,causing them to glow.

Figure 7.13 CRT.


Most CRT displays use a raster scan. A raster scan fires the electron stream ina series of zigzag lines that starts in the upper left-hand corner and moves left toright and top to bottom. It is repeated to maintain the image as the phosphor onlyglows for a short time. This is called refreshing. Interlaced monitors speed uprefreshing by first scanning the odd lines from top to bottom and then scanningthe even lines. However, this can cause the monitor to flicker. Non-interlacedmonitors refresh the screen by scanning every line at up to 72 times every second.When the screen is being altered, only the data that is changed is transmitted.Theinformation that describes the difference between the two screens is called deltainformation. It is the ‘change’ information.

A special type of CRT display is available to only display vector graphics.Vector display systems direct the electron stream to draw only the lines requiredfor the image. Shading can only be drawn as a series of lines. Vector displaysystems have a faster refresh rate than CRT displays using a raster scan.

LCDs (liquid crystal displays)are a flat screen. They consist of alayer of liquid crystal materialplaced between two polarisingsheets. Light is passed through theliquid crystal material, and currentis applied at particular points. LCDtechnology provides displays thatare very light, take up less room,produce no heat, have no glare, andcreate no radiation. Furthermore,LCDs require less power thanCRTs, allowing them to run onbatteries. At present, LCD tech-nology does not produce the samepicture quality as CRT technology,and larger displays are more ex-pensive. LCDs are used in portablecomputers (see Figure 7.14) andcan be mounted on the wall.

Touch screens enter data bydetecting the touch of the user’sfinger. The user’s finger interrupts amatrix of infrared light beamsshining horizontally and vertically across the screen. Touch screens do not allowfine precision of input and use big buttons or areas of the screen.

Projection devicesA data projection panel is a device that can be used together with a standardoverhead projector to project an image from the computer screen onto a wall orwhite screen. The projection panel uses LCD technology to display the imagefrom the computer. Light passes through the image much like a normal overheadprojection slide. Data projectors, which can take a video signal directly from a computer and project it onto a wall or screen, are also available. They are smaller and more versatile than a projection panel but are more expensive (seeFigure 7.15).

Figure 7.14 LCD screens used on portable computers.

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SpeakersSpeakers are devices used to produce sounds. Audio signals from a computer aretranslated into analog sound waves for transmission through the speakers. Thesound is generated electromagnetically. A coil of wire is attached to a cone ordiaphragm. The coil is placed around a permanent magnet, so that an electronicsignal passing through the coil magnetises it.As the coil is magnetised, it pulls andpushes against the permanent magnet, causing the cone to vibrate according tothe strength of the electronic signal.The movement of the cone makes the air nearthe cone vibrate, and this creates sound waves.

Head-up displaysHead-up displays are devices worn on the head to display information. They were originally developed for virtual reality. However, as the technology has been miniaturised, their application has widened. The heavy helmets have beenreplaced by displays no larger than a pair of glasses. In virtual reality, theparticipant watches himself or herself reacting to the environment. In othermultimedia systems, the display is projected onto the surface of the glasses. Theparticipant sees the display overlaying the real world.

Figure 7.15 A data projector.

IITT FFaaccttIT Fact‘There is no reason for any individual to have a computer in their home.’—Ken Olson, World Future Society Convention, 1977.

SoftwareThe software used for creating and displaying multimedia includes presentationsoftware, application software, authoring software, animation software, Webbrowsers and HTML editors.


Presentation softwarePresentation software is used to make a professional presentation to a group ofpeople. It improves the communication of information. A presentation consists ofa series of slides. A slide is an individual screen or page of the presentation. Eachslide may contain text, graphics, animation, audio and video. Some popularpresentation software programs include Microsoft PowerPoint, Lotus Freelanceand Aldus Persuasion.

Presentation software creates several documents that are used in a presenta-tion, such as on-screen presentations, audience handouts, overhead transparenciesand speaker’s notes:• On-screen presentations are slides displayed on a monitor or projected onto a

screen. The timing of the presentation is controlled either automatically ormanually. Automatic timing requires the user to set the timing for each slide;the slides then advance by themselves. Manual timing requires the user to clickthe mouse button to advance each slide.

• Audience handouts are images of two or more slides on a page. Handouts aregiven to people who attend the presentation.

• Overhead transparencies are slides printed as an overhead transparency inblack and white or in colour using either portrait or landscape orientation.

• Speaker’s notes are the notes the speaker needs when discussing the slides.A transition is a special effect used to change from one image or screen to

another. For example, one screen might slowly dissolve as the next screen comesinto view. In general, two or three transitions in a multimedia product willmaximise their impact on the audience. Transitions are frequently used in presen-tation software to allow a smooth change between slides (see Figure 7.16).

Figure 7.16 A transition design window in PowerPoint.

Application softwareApplication software is software used for a specific task. A variety of applicationsoftware is used in a multimedia system. It is often used to create the differenttypes of media in the multimedia system. Application software used in multi-media systems includes:

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• Word processors allow text to be entered and documents to be created. Thesuperior editing tools in word processors are used to write the text for amultimedia system. Some word processors can create documents that includeimages and sound.

• Spreadsheets use a rectangular grid made up of rows and columns to organiseand store data that requires some type of calculation. Spreadsheets are alsoused to produce different types of charts used in multimedia.

• Graphics software creates and edits images. A paint program creates a bit-mapped graphic. A drawing program creates a vector graphic. Images are oftencreated using advanced graphic tools in graphic software.

• Audio software creates and edits audio. Sounds are edited in many differentways, such as deleting sounds, changing the speed, adding a echo, overlaying(mixing) sound files and altering the quality of the sound file.

• Video software creates and edits video. It involves adding text, audio andimages to a video clip. Video software allows for a variety of effects, as well asthe ability to combine segments of different videos into one production. Aframe grabber captures and digitises images from a video. Frames can be cut,moved, cropped and pasted within the video.Adobe Premiere is an example ofvideo software (see Figure 7.17).

Figure 7.17 Adobe Premiere.

• Project management software is used to efficiently plan, manage and com-municate information on the development of a multimedia project. Projectmanagement software allows projects to be joined, tasks to be split amongteam members, and the project to be tracked over the Internet or via email.

Authoring softwareAuthoring software is used to combine text, graphics, animation, audio and videointo a multimedia product. The software allows the user to bring together theseparate media types. Authoring software allows the user to create interactivity. Itassigns relationships and actions for the different media elements using a scriptinglanguage. Most authoring software shares similar features and is capable ofcreating similar multimedia products. Popular authoring software includesMacromedia Director,Asymetrix Toolbook, Macromedia Authorware, HyperCard(see Figure 7.18) and HyperStudio.


Animation softwareAnimation software takes individual images and creates the illusion of move-ment. Remember that animation is just a series of images that are displayed inrapid succession. There are different types of animation software, such as two-dimensional (2D) animation, three-dimensional (3D) animation, and warping andmorphing.• 2D animation software uses flat two-dimensional images and combines them

to create the animation. Macromedia Flash is an example of 2D animationsoftware.

• 3D animation software uses a mathematical model of a three-dimensionalobject to realistically portray objects with depth. It is a common element inmany movies made today.

• Warping and morphing software is used to create special effects using a rangeof powerful tools.

Web browsersA Web browser is a software program stored on a computer that allows access tothe Web. It will display a Web site if the address (or location) is entered directlyinto the browser. Web browsers will receive multimedia files that are embeddedin a Web page. Web pages that have multimedia files take longer to download, asthey are larger in size. However, developments in technology are continuallyimproving the quality and speed of images, audio and video over the Internet.Some popular Web browsers include Netscape Navigator and Microsoft InternetExplorer. Both browsers will display a variety of images and can play audio andvideo with the appropriate additional software (plug-ins).

HTML editorsWeb pages are created using hypertext markup language (HTML). HTML is a set of special instructions (called tags) that indicate how parts of a document willbe displayed. An HTML editor is a software program that specialises in writingHTML code. Instructions in HTML are given using HTML tags. Tags aremetadata, or information about data.A tag consists of a left angle bracket (<), a tagname and a right angle bracket (>). Tags are usually paired such as <TITLE> and</TITLE> to start and end the tag instruction.The end tag looks like the start tagexcept a slash (/) precedes the text within the brackets. Every HTML documentcontains certain standard tags, such as <HEAD> and <BODY>. (See Figure 7.19.)

Figure 7.18 HyperCard.

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Figure 7.19 An HTML document.

<HTML>

</HEAD>

<TITLE>sample HTML</TITLE>

<BODY BGCOLOR="#FFFFFF">

<H1><CENTER>Pet World</CENTER></H1>

<H3><CENTER>Dogs</CENTER></H3>

<CENTER><TABLE BORDER=1>

<TR>

<TD WIDTH=107>

<P><IMG SRC="dog.gif" WIDTH=94 HEIGHT=183 ALIGN=middle></P>

</TD>

<TD>

<P>Click on the large image to find out more about this breed of dog.

Click on the sound icon to hear the dog barking, or click on the movie

icon to see the dog running.</P>

</TD>

<TD>

<P><IMG SRC="DOGRUN.GIF" WIDTH=200 HEIGHT=35 ALIGN=bottom></P>

<P><IMG SRC="sound.gif" WIDTH=119 HEIGHT=86 ALIGN=bottom></P>

</BODY>

</HTML>

1 How does a CRT display produce images?

2 What is a cross fade?

3 Explain the difference between a CRT display that uses a raster scan and one thatuses a vector display system.

4 Describe an interlaced monitor.

5 How does an LCD display produce images?

6 Describe a data projection panel.

7 How is sound generated in a speaker?

8 Describe some of the documents that can be created using presentation software.

9 List the application software used in a multimedia system. What type of data doeseach type of application software create?

10 What is authoring software?

11 List three different types of animation software.

12 How are Web browsers related to multimedia?

LEARNING ACTIVITIES

1 A multimedia presentation is to be created on the requirements of the HSC. Thepresentation requires handouts for the audience. What software would youchoose? Why? Describe the processes you would use to create the presentation.

2 Copy and complete Table 7.5 on page 245 by listing the software that is readilyavailable to create the types of media listed in the first column. If possible, createa sample file using this software.

Exercise 7.3


7.4 Other information processesAll information processes play a role in multimedia systems, including collecting,organising, processing, and storing and retrieving.

CollectingCollecting for a multimedia system may involve a range of tasks, such as writingthe text, drawing images, recording and editing audio files, recording video tracks,or gathering data from the Internet. It is important to correctly identify the sourceand verify the accuracy of any information collected. A range of hardware col-lection devices is used to collect different media types for a multimedia product.

Methods for digitisingScanners are input devices that can electronically capture text or images, such asphotographs and drawings.The scanner converts the text or image into digital datathat can be processed by the computer. The digital data can be printed, edited ormerged into another document. Scanners offer a range of different resolutions,such as 2400 dpi, 4800 dpi and 9600 dpi. The higher the resolution, the betterthe quality of the final output. Scanners may be single-pass (scans only once) or multiple-pass (scans for each colour). They use a software standard calledTWAIN (Technology Without An Interesting Name) that allows the digital imageto be used in a range of different applications. There are three common types of scanners:

3 Use audio software and record sound at several different settings. Compare thequality of the files with the size of the files.

4 Create a multimedia presentation on the content of this chapter (multimedia).a Use different media types in the presentation.b Apply good design to the presentation.c Create a handout of your presentation.d Show the presentation to the class.

5 Review another group’s multimedia presentation from question 4.a How effective is the use of the different media types?b Does the multimedia add to the presentation?c Does the use of image, audio or video detract from the information being

presented?d Outline the design principles applied in the presentation.e What system has been used to help navigate the presentation?

Media Name of software Default file formatText

Audio

Bit-mapped graphic

Vector graphic

Animation

Video

Table 7.5 Types of media.

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• Hand-held scanners enter text and imagesthat are less than a page wide. The hand isused to make a pass of the document. Hand-held scanners are adequate for small picturesand photos but cannot easily capture anentire page. Software is used to join scanneditems to make a full page.

• Flatbed scanners look similar to a smallphotocopier.The document remains flat andstationary during the scanning (see Figure7.20).

• Overhead scanners look like an overheadprojector. Documents are placed face up onthe scanning bed, and a small overheadtower moves across the page.Digital cameras are input devices that capture and store images in digital form

rather than on film. They contain a viewfinder, a lens to focus the image and astorage medium, such as a memory card, hard disk drive or floppy disk, to retainthe images. After a picture is taken, it is transferred to a computer and can bemanipulated using graphics software. Digital photos are limited by the amount ofmemory in the camera, the quality of the lens and the output device. The mainadvantage of digital cameras is that making the photos is both inexpensive and fastbecause there is no film processing. Most digital cameras compress and save theirimages in standard JPEG or FlashPix format.

Video cameras are used to create a videoclip in analog or digital form. Analog form ina super VHS format is converted into digitalform using a video capture card, whichinterprets each frame of the video as a bit-mapped image. Video capture cardscompress the video clip by using acompression algorithm that analyses thechanges from one frame to the next. Theyencode the starting frame and a sequence ofdifferences between the frames. Digitalvideo cameras are input devices that capturevideo in a compressed digital format, such asMPEG. These video files are transferreddirectly to a computer (see Figure 7.21).

A VCR (video cassette recorder) is usedto select footage from existing videotapes.The final product may also be placed on avideotape for use.A composite video systemsends all the video information using onesignal. The RCA phono connector iscommonly used for composite video on

VCRs and video cameras. Professional-quality video systems produce two separatesignals: one for colour and one for brightness. Video equipment in Australia mustconform to the PAL system, whereas the USA system is called NTSC. A videodigitiser takes the signal from a single-frame video or videos with a freeze framesignal. A frame grabber captures and digitises images from a video. The rate ofcapture may vary, but usually video frames display at around 30 per second, so a

Figure 7.20 Flatbed scanner.

Figure 7.21 Video camera collecting data on road users.


freeze frame or frame grabbersystem operates by grabbing animage that lasts for 1/30th of asecond.

Microphones are input devicesthat capture sound. Sound travelsthrough the air in waves and isanalog data. Audio is sound thathas been digitised. A sound cardtransforms the sounds from amicrophone into audio. Sound-Blaster cards are a standard fordigital audio on a personal com-puter (see Figure 7.22). They arecapable of recording and playingdigital audio at 44.1 kHz stereo,or CD-quality sound. Sound cardssupport a MIDI sequence. Thisallows a musician to use a MIDIinstrument to play music while thecomputer can store and edit themusic. Sound may be recordedonto the computer directly orimported from storage systemslocated on the Internet or on optical disks.

OrganisingA script and a storyboard are two tools used to organise a multimedia product. Ascript is a printout of all the text, graphics, animation, audio and video used in theproduction. It outlines the interactivity in the project.A script gives directions forthe construction of the multimedia product. It is a textual method of representingideas and actions. On the other hand, a storyboard is a visual method.

StoryboardA storyboard is a series of frames each representing a different action or screenimage. It is based on the traditional cartoonist storyboard where the cartoonistsketches each frame of the cartoon. Storyboards are drawn on paper and fre-quently edited. They define each screen and the specific media types of themultimedia product. Storyboards consist of navigation paths, information andgraphics. They are popular because they are simple to construct, easy to read and can be modified at every stage.

There are four storyboard layouts: (Figure 7.23):• linear layout—a simple sequential path that is set up quickly• hierarchical layout—a sequential path in a top-down design in which the user

starts at the beginning and moves down through the multimedia product• non-linear layout—no structure; the user moves between different layouts in

any direction• combination layout—a blending of the above layouts.

Figure 7.22 Sound card being inserted into a PC.

248 Options

ProcessingProcessing data for a multimedia system is the manipulation of the data. Itinvolves the integration of data, compression of data and hypermedia.

Integration of dataAfter the data is collected, it is often imported into multimedia software.Multimedia software is used to integrate text, number, image, animation, audioand video data. It allows the user to bring together the separate media types.Multimedia software will accept different media types in a variety of formats. Italso allows the user to create interactivity.

Compression and decompressionMultimedia products are characterised by large file sizes. This is the result ofimporting large graphics, animation, audio, or video files. Compression reduces thenumber of bits required to represent information. It allows the user to store moredata and makes data transfer faster. Compressed data must be decompressed toextract the original information. There are a number of standard compressed fileformats for different media, such as JPEG for images and MPEG for video.

The use of compressed file formats is very common in multimedia systems.Images are often stored in GIF or JPEG formats. The major difference betweenthese formats is the colour support. GIF files are limited to 256 colours, whereasJPEG images can use the full spectrum of 16.7 million colours. Images are createdusing graphics software and saved using one of these formats. This allows them tobe easily imported into an authoring program.

combination

non-linear

hierarchical

linear

Figure 7.23 Storyboard layouts.


A CODEC (coder-decoder, pronounced ‘ko-dek’) is used to encode anddecode (or compress and decompress) various types of data. It is typically used forsound and video files. CODECs convert analog video signals into compressedvideo files, such as MPEG, or analog sound signals into digitised sound, such asRealAudio. The CODEC’s video compression algorithm uses the fact that thereare usually only small changes from one frame to the next to select the data thatcan be ‘discarded’ during compression. It encodes the starting frame and asequence of differences between frames. CODECs are also used with streaming(live video or audio).

HypermediaHypermedia involves the linking of information in different types of media. Theinformation is stored using a set of documents that may contain text, images,audio, video or executable programs. Each document is independent, and infor-mation is retrieved using hypertext. All the various forms of information arelinked together to provide an easy way to navigate. The most well-knownapplication of hypermedia and hypertext is the Web.

IITT FFaaccttIT FactClick streaming is a technique used to study how individual users navigatea Web site by recording where they click. Web page designers use it to seehow users are accessing their page and what areas are of interest to thevisitor.

Storing and retrievingPeople need efficient methods for the storage and retrieval of information from amultimedia product. These methods involve different compression techniquesand file formats.

Compression techniquesCompressing files increases the storage efficiency.The amount a file is compressedis measured by the compression ratio.The compression ratio describes how muchsmaller the compressed file is compared to the uncompressed file. If a compressedfile is half the size of the uncompressed file, the compression ratio is 2 to 1 (2:1).That is, two units of data in the uncompressed file equal one unit of data in thecompressed file.A higher compression ratio indicates greater compression of data.For example, a compression ratio of 3:1 means the file is more compressed than afile with a compression ratio of 2:1. A compression ratio of 1:1 indicates the filehas not been compressed at all.

The two basic types of compression are called lossy and lossless:• Lossy compression removes a number of data bytes from the file.The resulting

file is smaller in size but the quality is reduced. However, audio and video filescan be compressed with high compression ratios and without any changenoticeable to the human ear or eye. For example, an MPEG file can provide acompression ratio up to 200:1.

• Lossless compression allows the original file to be recovered in full. It works byreplacing repeated data with something that takes up less room. For example,

in this book the word ‘and’ appears many times. If each ‘and’ is replaced witha one-character symbol or token, two-thirds of the space required by the word‘and’ is saved. Lossless compression is used mainly on text files, such as wordprocessing, spreadsheet and database files. Each file of a given type can have adifferent compression ratio depending on the contents of the file. A text fileusually has a compression ratio of 3:1.

File formatsIt is important to choose an appropriate file format for each type of media. Theapplication software and the quality of the data will influence the file format.Thetype of multimedia product will also influence the file format. For example, if you were using a Web browser, then images would usually be saved as GIF orJPEG files. If the multimedia product is to be played as a stand-alone product,then it must be saved as an application or provided with a player program. It isalso important to store all files on a convenient storage device, such as removablecartridges (Zip or Jaz disks), optical disks (CD or DVD), flash memory orvideotape.

There are many different file formats used for multimedia. These formats areconstantly changing, and new formats are being developed:• ASCII (American Standard Code for Information Interchange, pronounced

‘ass-kee’), or TXT (text), format is a standard format for storing text andnumeric data. The data is essentially raw text without any formatting. Eachbyte in the file contains one character that conforms to the standard ASCIIcode. Most applications can store data in ASCII format.

• RTF (Rich Text Format) is a standard developed by Microsoft for specifyingthe format of text documents. RTF files are actually ACSII files with specialcommands to indicate the formatting of characters and paragraphs.

• HTML (Hypertext Markup Language) is used to create documents for theWeb. It uses a set of special instructions (called tags) that indicate how parts ofa document will be displayed.

• BMP (Bit-map) is the native bit-mapped graphic format for Microsoft Win-dows. The images displayed when Windows starts and the wallpaper used onthe desktop are in BMP format. BMP tends to store graphical data inefficientlywith larger file sizes than other graphic file formats.

• JPEG (Joint Photographic Experts Group, pronounced ‘jay-peg’) stores bit-mapped graphics. JPEG files are compressed with a compression ratio of up to100:1. However, JPEG uses lossy compression, so some data is lost during theprocess of compression. JPEG format is a popular choice for the Web. It is bestused for photos and continuous tone images. JPEG images can use the fullspectrum of 16.7 million colours.

• GIF (Graphics Interchange Format) stores bit-mapped graphics. It was devel-oped as the predominant format for Web graphics. GIF files can be compressedto reduce size without loss of quality (lossless compression). It is best used forline-art drawings, logos and simple graphics. GIF compresses graphics filesusing 8-bit colour (256 colours) and achieves a compression ratio of 2:1.

250 Options


• TIFF (Tagged Image File Format) stores bit-mapped graphics. It is widelysupported by applications on both Windows and Macintosh platforms. Somecaution needs to be used when transferring TIFF files across platforms as thereare several variants, some of which involve compression.

• PICT (Picture) stores bit-mapped or vector graphics. It is the standard graphicsfile format on Macintosh computers. PICT files are encoded in QuickDrawcommands and can also be used on IBM-compatible computers.

• EPS (Encapsulated Postscript) stores vector graphics. Postscript is a printerlanguage that is used for high-end publishing. This format is commonly usedfor files that will be output on high-resolution devices. EPS files are not vieweddirectly on the screen (see Figure 7.24).

IITT FFaaccttIT FactA GIF image appears on a Web page in a rough format at first, and then later,as the page completes loading, becomes clearer and sharper. This methodkeeps the viewer interested in the image that is being formatted and makesthe process seem shorter.

Figure 7.24 Software to convert EPS files.

• WMF (Windows Metafile Format) stores bit-mapped or vector graphics. TheWMF file format is commonly used by Microsoft Windows applications.WMFis used to exchange images between Windows applications.

• CGM (Computer Graphics Metafile) stores vector graphics. It was designed byseveral standards organisations to become the standard vector graphics fileformat. It is supported by a wide variety of software and hardware products.

• WAV (pronounced ‘wave’) stores either 8-bit or 16-bit sound. It was developedjointly by Microsoft and IBM and built into Windows. One disadvantage withWAV sound files is that they require a large file size. For example, a ten-minuteCD-audio sound file will require over 100 Mb.

252 Options

• RealAudio is a de facto standard for exchanging sound files over the Internet.It was developed by RealNetworks and supports FM-stereo quality sound. ARealAudio player is required to hear a RealAudio sound file on a Web page.Web browsers such as Internet Explorer and Netscape Navigator include aRealAudio player.

• AIFF (Audio Interchange File Format) stores 8-bit digitised sound files. It is asound file format developed by Apple.

• MIDI (Musical Instrument DigitalInterface, pronounced ‘middy’) is a standardconnection for computers and elec-tronicmusical instruments. A musician uses a MIDIinstrument to play music and uses thecomputer to store and edit the music (seeFigure 7.25). MIDI allows 16 instruments tobe played simultaneously from MIDI inter-faces. The sound is recorded in a file formatcalled the MIDI sequence. MIDI files requireless storage as they only contain the noteinformation and not details of the soundwave. The quality of the sound from MIDIfiles is dependent on the synthesiser.• MP3 (MPEG Audio Layer 3) is an audiocompression technology that is part ofMPEG-1 and MPEG-2 (discussed below). Itcompresses CD-quality sound using acompression ratio of 11:1. MP3 has made itpossible to download quality audio from theInternet (see Figure 7.26). For example, afour-minute song that would normally

require 44 Mb of storage will be compressedusing MP3 to only 4 Mb. MP3 compresses afile by removing the high and low frequenciesout of human hearing range.

• MPEG (Motion Picture Expert Group, pronounced ‘em-peg’) is a family offormats for compressed video that has become a standard. MPEG files achievea high compression ratio by using lossy compression and only storing thechanges from one video frame to another. MPEG-1 standard provides a videoresolution of 353 x 240 at 30 fps. It is similar to the quality of conventionalVCR videos. MPEG-2 standard offers resolutions up to 1280 x 720 and 60 fps.It is sufficient for all major TV standards and is used on DVDs.

• QuickTime is a video and animation format developed by Apple Computer. Itis built into the Macintosh operating system and can be used with mostMacintosh applications. Apple has produced a QuickTime version forWindows.

• Animated GIF (Graphics Interchange Format) is a type of GIF image that canbe animated. Animated GIF does not give the same level of control as otheranimation formats but is supported by all Web browsers.

Figure 7.25 Artist recording music in MIDI format.


Figure 7.26 Web site for MP3.

1 Describe three common types of scanners.

2 What is the main advantage of digital cameras?

3 How does a video capture card work?

4 What is a composite video system?

5 What is the usual rate at which a frame grabber captures an image?

6 Describe four storyboard layouts.

7 What is compression?

8 Describe the major difference between GIF and JPEG file formats.

9 What is the purpose of a CODEC?

10 What is hypermedia?

11 Explain the difference between lossy and lossless compression.

12 What is the difference between an ASCII file and an RTF file?

13 Describe the JPEG file format.

14 Describe the EPS file format.

15 Outline the major difference between MIDI and digital waveform sound files, suchas WAV.

16 Why is MP3 an important file format?

17 Describe two common file formats for video.

LEARNING ACTIVITIES

1 A multimedia production is to be created about your family. What storyboardlayout would be appropriate? Give reasons for your answer. Construct astoryboard for your family.

Exercise 7.4

254 Options

7.5 Issues related to multimediasystemsBoth positive and negative impacts arise from the use of multimedia systems. Inthis section, we examine some of the issues raised by multimedia systems.

CopyrightCopyright is the right to use, copy or control the work of authors and artists. It isagainst the law to break copyright.You are not allowed to use or copy the work ofanother person without the person’s permission. Data collected from the Internetis usually protected by copyright.Text, images, video or animations obtained froma Web site should not be used without acknowledgment or permission from theowner. However, the Copyright Act does make special provisions for students touse information for research purposes. It allows students to use a reasonableportion of the original work if correctly cited. When citing an Internet source,include the following information:• author’s surname and initial or organisation’s name

2 A multimedia production is to be available on CD-ROM and via the Internet. Whataudio and video formats would you choose? Justify your decision. Do theseformats require additional plug-ins?

3 Investigate the current compression formats for video, audio and image files.Outline the advantages of these formats. Present the results of your investigationto the class.

4 Create an image using a paint program and a draw program:a Convert the image to a different resolution and compare the file sizes.b Convert the image to a different file format and compare the file sizes.

5 A group of students intends to develop a multimedia production about theirschool. It is to be displayed on the Web. Outline any problems for users of the Website if the multimedia production is developed using a linear layout. What story-board layout would you suggest for these students?

6 You have been asked to put together a multimedia presentation for a well-knowncharity. They are holding a dinner and auction and want to show images of theirwork during the meal:a Describe the hardware you would use to collect information.b Describe the application software you would use to create or capture the

information.c List the file formats you would use to store the different types of media.d Describe the hardware you would need to display the presentation.e Describe the software you would use to display the presentation.

7 A music store is planning an interactive multimedia Web site of the latest CDreleases using all the media types. The Web site is to include selected songs,historical data about the artists, photos and interviews. Work in groups tocomplete the following tasks:a Write a storyboard layout for the multimedia display.b Describe the design features you would use in the production.c Design a home screen for this display.d Develop the multimedia product for the Web.


• title of the completed work or Web page• URL of the page• date of document or Web page publication• download date.

The copyright issue is highlighted with music files. It is legal to rip (thetechnical term for transferring songs from standard audio to MP3 format) musicfrom your own CDs. It is also legal to download music from Web sites where theartists own the rights. However, playing or distributing any other music files isbreaking the copyright law. Even if you listen to streamed music from a Web site,the original artist must give permission. The copyright law aims to protect theoriginal artist for creating the piece of music.

The issue of copyright is a moral issue. Is it right to copy the original work ofan author or artist without their permission? Authors or artists often spendhundreds of hours developing a product and deserve some return for their efforts.The fact that it is relatively easy for anyone with a computer to make copies of theproduct is irrelevant. If people infringe copyright, authors and artists are notgetting royalties and they will be reluctant to spend time developing goodproducts.We should take care when downloading files to ensure that they are freeto download or that licensing fees have been paid.

Appropriate use of the InternetNew developments on the Internetare creating a range of differentissues. The introduction of livevideo data raises the issue ofprivacy. Privacy is the ability of anindividual to control personal data.Digital video cameras are beinglocated in streets and streamed liveon the Internet (see Figure 7.27).People who are walking down thestreet are not aware they are beingphotographed nor have they givenpermission to be presented on thevideo. Is our personal privacy beinginvaded? Will all aspects of ourlives, such as work, be streamedonto the Internet? How can ourprivacy be protected from this newdevelopment?

Merging technologiesThe merging of different technologies is a trend occurring at a staggering rate.Today, communication capabilities are essential for a computer system andcomputer technology is essential for communication.When people buy a personalcomputer, they purchase a modem and connect it to a phone line to access theInternet. Similarly, telephones have become data entry terminals into computersystems. Organisations are asking individuals to make choices using the keypad onthe telephone. Radio, television and the Internet are converging. An increasingnumber of Web sites are providing radio and video broadcasts (see Figure 7.28).Will the Internet replace radio and television?

Figure 7.27 Live video on www.coastalwatch.com.

256 Options

Advances and cost reductions in processing speeds, storage capacities,miniaturisation, file compression, and the speed of electrical components havemade the use of digital data more affordable. Digital data is represented in theform of digits or numbers and is used by computer technology.The digitisation ofdata provides the opportunity to use computer technology. Advances indigitisation have made the extensive use of multimedia feasible. A few years agoit was not possible for personal computers to combine different types of data. Oneexample of the benefits of digitisation is digital television.

Digital television systems are designed to present interactive multimedia.Theymerge communication, television and computer technologies. Digital televisionwill offer more channel choices, a higher resolution screen and greater control overthe program the user is watching. For example, a user watching a football matchcan choose to watch a particular football player.

Figure 7.28 Radio on the Internet.

IITT FFaaccttIT Fact‘The danger from computers is not that they will eventually get as smart asmen, but that we will meanwhile agree to meet them halfway.’—BernardAvishai from ‘Charades,’ an Internet collection of quotations.

Data integrityData integrity describes the reliability of the data. It involves the accuracy,currency and relevance of the data. There is no guarantee of the integrity of datain multimedia systems. The source of any data needs to be cross-referenced. TheInternet is an obvious way of cross-referencing data obtained from a multimediasystem. However, the Internet does not always provide accurate data. Dataintegrity raises a number of issues. Who is responsible for the accuracy of theinformation? Is the creator the only person responsible for the accuracy of the data? Do organisations that provide access to information in a multimedia


system have a responsibility to verify its accuracy? Responsible users must takecare when obtaining information from multimedia systems. Clearly, it is necessaryto compare data from a number of sources to determine which data is accurate.

1 What is protected by the copyright law?

2 List the information needed to correctly cite an Internet source.

3 How does the copyright issue apply to music files?

4 Why is copyright a moral issue?

5 How is live video on the Internet an issue?

6 Describe the merging of computer technology and communication.

7 What advances in technology have made digital data more affordable?

8 List some of the advantages of digital television.

9 Why is data integrity an ethical issue?

LEARNING ACTIVITIES

1 Multimedia systems are having a positive and negative impact on our society.Briefly describe some of the changes to our society caused by multimedia systems.

2 Active billboards combined with wireless Internet could allow people to orderitems from their car. What issues do you see with this concept? Do you think thisconcept will develop in the future? Why?

3 A friend downloaded a multimedia presentation from the Internet and submittedit to the teacher as her own work. Why is this an ethical issue? What can be doneto stop this practise? Would you take any action? Why?

4 Developments in technology have made huge changes to multimedia systems inthe past five years. Predict some possible changes to multimedia productions inthe next five years. Justify your predictions.

5 Locate and download an MP3 format file with no copyright from the Internet.Describe this process. What software do you need to play these files on acomputer? Why are musicians and recording companies worried about the MP3format? Is downloading a song from a Web site the same as stealing? Give reasonsfor your answer.

6 You have been asked to update the design of a school Web site. The multimediasite is to contain some images of the school grounds, staff lists, email contacts forthe school, information about courses, samples of student work and photos ofschool activities.a What privacy issues do you need to consider when showing images of staff or

students?b How would you ensure that all work displayed is original?

Exercise 7.5

258 Options



1 Which of the following is not a type ofmedia used in a multimedia product:A textB hypertextC videoD interactivity

2 To produce realistic animation, framesmust be displayed at close to:A 5 frames per secondB 5 frames per minuteC 30 frames per secondD 30 frames per minute

3 Tweening involves:A a computer generating intermediate

frames between two objectsB an artist drawing each frame indi-

viduallyC using cartoon characters in an ani-

mationD creating a path between two objects

4 Morphing is:A changing one image into another

imageB changing the appearance of one

imageC changing the resolution of an imageD changing the colour depth of an

image

5 The storage requirements for bit-mapped graphics will increase if the:A number of colours increasesB resolution increases

C bit depth increasesD all of the above

6 A content provider:A designs the presentationB often works as project managerC supplies the material for a presen-

tationD converts the raw material into digital

format

7 Virtual reality enables a person to:A interact with an artificial environ-

mentB interact with the real environmentC select real data for a multimedia

productD select the content of the information

8 Which of the following software is notused to create a multimedia product:A authoring softwareB word processingC graphics softwareD Web browser

9 When saved to disk, sound may bestored as:A WAV, MP3 or RealAudioB WAV, MPEG or MIDIC JPEG, RealAudio or MIDID JPEG, MPEG or MP3

10 The most common file format for com-pressed digitised video is:A JPEGB MPEGC GIFD MP3


PART B


Statements

1 The legal right to ownership of a work.

2 Pictures, such as drawings, paintings orphotographs.

3 The number of bits per pixel.

4 Sound that has been digitised.

5 A file format for images that uses lossycompression.

6 It is used to create documents on theWeb.

7 A file format for images that uses 8-bitcolour (256 colours).

8 A graphic that is made up of objects,such as a straight line, curve or shape.

9 A link between two parts of a multi-media product.

10 An audio file format developed byMPEG.

11 A display that is produced by firing astream of electrons onto the inside ofthe screen.

12 A device that captures and digitisesimages from a video.

13 The number of times a sample is takenfrom the sound wave.

14 A graphic that treats each pixel on thescreen individually and represents thisby bits in memory.

15 A type of medium that starts with acontinuous event and breaks it intodiscrete frames.

16 The number of bits per sample.

List of terms

a frame grabber

b hotword

c audio

d video

e HTML

f sample size

g GIF

h copyright

i bit-mapped

j vector

k CRT

l JPEG

m image

n MP3

o bit depth

p sampling rate

PART C


1 Describe the different types of mediaused in a multimedia product.

2 Compare a multimedia presentation to a paper-based presentation. Giveadvantages and disadvantages for eachversion.

3 You have been employed as a projectmanager for a multimedia game designteam.a What is your role in the production?b Describe the roles of the other mem-

bers of the team.c Describe the hardware and software

you will use.

4 Your school is planning a new Web site. You have been given the job ofdesigning the site from scratch with ateam of other students.a What features would you describe as

essential for this site?b Develop a storyboard for the site.c Give reasons for your choice of story-

board layout.d Describe your navigation system.e Describe the ethical issues that need

to be considered before addingstudent photos to the site.

Chapter review

260 Glossary

analog-to-digital converter (ADC) A device thattakes an analog signal, such as a voltage or electriccurrent, and electronically converts it into digitaldata.

absolute referencing Copying a formula in aspreadsheet where the contents of the formula inthe source cell do not change when pasted into thedestination cell. Absolute references are indicatedby a $ sign. (e.g., $B$5).

access See data access.accuracy See data accuracy.actuator A display device in an automated

manufacturing system that performs a mechanicalaction under the control of a signal from a controller.

aliasing A staircase pattern created when a bit-mapped graphic is enlarged.

analog data Data represented by using continuousvariable physical quantities, such as voltages.

analysing The information process that involves theinterpretation of data, transforming it intoinformation.

analysis report A report that contains details of thenew system with recommendations for design,implementation and maintenance.

animation The movement of a graphic, as in acartoon, accomplished by presenting a series of stillimages in rapid succession.

animation software Software that takes individualimages and creates the illusion of movement.

ascending order Data arranged from smallest tolargest (0 to 9) or from first to last (A to Z).

assembly line production A series of workstationsconnected by a transfer system that moves partsbetween each workstation.

asynchronous transmission Serial transmissionmethod that sends one byte at a time with specialstart and stop bits before and after each byte ofdata.

atomicity A property of a transaction processingsystem that ensures that all of the steps involved ina transaction are completed successfully as a group.

attachment A file sent with an email message.attribute A defined property of an entity in a

relational database.audio Sound that has been digitised.audio conference A single telephone call involving

three or more people at different locations.authoring software Software used to combine text,

graphics, animation, audio and video into amultimedia product.

automated manufacturing system An informationsystem involved in production by inventorytracking, record-keeping, production schedulingand actual production.

automated warehouse A storage facility that usesautomatic control for the storage of products.

automation The application of automatic control toindustrial processes. It refers to the application ofmachines to tasks once performed by humanbeings.

backup A copy of data or software for the purposeof safety. It is used to rebuild a system.

backward chaining An inference strategy that startswith one or more possible solutions and searchesback through the system to determine thequestions to be asked.

bandwidth The capacity of a channel, ortransmission medium, to transfer data.

barcode reader An input device that enters productidentification at a point-of-sale terminal.

baseband A network that uses the entire capacityof the cable to transmit only one signal at a time.

batch system An automated manufacturing systemthat produces a specific quantity of a product.

batch transaction processing A transactionprocessing method that collects transaction data asa group, or batch, and processes it later.

baud rate The maximum number of data symbolsor electrical signals that can be transmitted in onesecond.

bias Data that is unfairly skewed or gives too muchweight to a particular result.

biometric device A device that uses personalcharacteristics, such as fingerprints, hand size,signature, eye and voice, to gain access to aninformation system.

bit depth The number of bits per pixel for animage.

bit mapping The relationship between the imageand the bits in memory. Also called memorymapping.

bit-mapped graphic A graphic that treats each pixelon the screen individually and represents this bybits in memory.

bit rate See bits per second.bits per second (bps) A unit of measurement for the

speed of data transfer. It is the number of bits thatcan be transmitted in one second. Also called bit rate.

block diagram A diagram used to represent asystem.

bridge A combination of hardware and softwareused to link two similar networks.

broadband A network that divides the cable so thatseveral signals can be transmitted at the same time.

bus A pathway of wires and connectors thatprovides the link between input, storage, processand output devices.

bus topology A network topology where all thedevices are attached to a direct line called a bus.

computer-aided design (CAD) The use ofinformation technology to design and analyse aproduct or object.

Glossary

Glossary

computer-aided manufacturing (CAM) The use ofspecialised information technology tools toautomate the entire manufacturing process.

computer-based training (CBT) A type ofmultimedia product used for education andtraining.

cell The intersection of a row and column in aspreadsheet. Also a frame or still image used in ananimation sequence.

cell reference The position of the cell in thespreadsheet.

cell-based animation Animation that involvesdrawing and displaying individual frames or cells.

character The smallest unit of data that people canhandle. It is a single letter, number, punctuationmark, or special symbol that can be displayed onthe screen.

chart A graphical representation of numerical data.Types of charts typically include bar (histogram),column (stacked bar), line (continuous) and pie(sector).

checksum A method of checking for errors in datatransmission by counting the number of bits in adata packet.

computer-integrated manufacturing (CIM) Anautomated manufacturing system that involves allthe engineering functions of CAD/CAM, as well asthe business functions of the organisation.

circular reference A formula in a spreadsheet thatrefers to itself, either directly or indirectly.

client-server architecture The software relationshipbetween the client (user) and server.

coaxial cable A cable consisting of a single copperwire surrounded by an insulator, groundedshielding and an outer insulator.

coder-decoder (CODEC) A method used toencode and decode (or compress and decompress)various types of data.

collecting The information process that involvesdeciding what to collect, locating it and collectingit.

communication system An information system thatenables people to send and receive data andinformation.

composite key A key in a database that is made byjoining two or more fields together. It is used whenno data item in any field can be guaranteed to beunique. Also called compound key.

composite video A system that sends all the videoinformation using one signal.

compression See data compression.compression ratio A measurement of the amount a

file has been compressed.computer operator A person who performs tasks

on the computer equipment, such as monitoringperformance, starting up, running jobs and backing up.

concurrency A property of a transaction processingsystem that ensures two users cannot change thesame data at the same time.

constraint A factor that affects an informationsystem and prevents it from achieving theobjectives.

context diagram A graphical method ofrepresenting an information system using only asingle process together with inputs and outputs(external entities).

continuous system An automated manufacturingsystem capable of operating 24 hours per day forweeks or months without stopping.

controller A device in an automated manufacturingsystem that receives data from a sensor andchanges it into information that can be used by thesystem.

copyright The right to use, copy or control the workof authors and artists, including softwaredevelopers.

cyclic redundancy check (CRC) A method ofchecking for errors in data transmission using adivision process.

critical damping Damping at the preferred rate ofchange in the output of the system.

cathode ray tube (CRT) A type of screen thatproduce images by firing a stream of electrons ontothe inside of the screen, which is coated with tinydots, or pixels, made of phosphor.

carrier sense multiple access and collision detection(CSMA/CD) A method to avoid collisions on anethernet network where all nodes have the abilityto sense signals.

custom software Application software written byprogrammers using the exact specifications for thenew system.

damping The process in an automatedmanufacturing system that modifies the signal tothe output device based on the input signal.

data The raw material entered into the informationsystem.

data access The extent to which data is available topeople.

data accuracy The extent to which data is free fromerrors.

data bits The number of bits in each group of data.data compression A data storage technique that

reduces the number of bits required to representinformation.

data dictionary A comprehensive description ofeach field (attribute) in a database.

data encryption The process of encoding data. It isthe most effective way to achieve data securityduring the transmission of data.

data flow diagram (DFD) A graphical method ofrepresenting an information system using a numberof processes together with inputs, outputs andstorage.

data integrity The reliability of the data.data mart A smaller version of a data warehouse

used to store data about a specific topic or area.data mining A process that finds relationships and

patterns in the data stored in a database.

261

262 Glossary

data modelling The process of identifying entities,the relationships between those entities and theattributes of those entities in a relational database.

data ownership An ethical issue related to whoowns and controls data about an individualcollected by another individual or organisation.

data projection panel A display device that can beused together with a standard overhead projectorto project an image from the computer screen ontoa wall or white screen.

data redundancy The undesirable duplication ofdata within a database.

data security A series of safeguards to protect data.data type The kind of data, such as image, audio,

video, text or numbers, that can be stored in adatabase field.

data validation The checking of the accuracy of thedata before it is processed into information.

data warehouse A database that collectsinformation from different data sources.

database An organised collection of data.database information system An information

system that uses a database.database management system (DBMS) A software

package that builds, maintains, and provides accessto a database.

database of facts Data in an expert system thatrelates to the specific situation being analysed.

decision support system (DSS) An informationsystem that assists people to make decisions byproviding information, models and analysis tools.

decision table A table that represents all possibleconditions and actions. It indicates the alternativesfor different conditions and actions based on therules.

decision tree A diagrammatic way of representingall possible combinations of decisions and theirresulting actions. It represents the decisions madewithin a system as the branches of a tree.

decoding The conversion of data from the formused for transmission back to its original form.

descending order Data arranged from largest tosmallest (9 to 0) or from last to first (Z to A).

digital camera An input device that captures andstores images in digital form rather than on film.

digital data Data that is represented in the form ofdigits or numbers.

direct access A method of retrieving data thatallows data to be found directly, without accessingall the previous data.

direct conversion Conversion to a new systeminvolving the immediate change to the new systemon a chosen date and the discontinuation of the oldsystem.

discrete system An automated manufacturingsystem that performs a single task in a small timeinterval.

displaying The information process that presentsthe output from an information system to meet agiven purpose.

distributed database A database located at morethan one site that acts as a single collection of databut is geographically dispersed.

documentation A written description to explain thedevelopment and operation of an informationsystem.

domain name The address of a specific computeron the Internet.

downloading The action of receiving a file fromanother computer.

electronic mail (email) A messaging system thatallows the sending and receiving of electronicmessages using a computer.

encoding The conversion of data from its originalform into another form for transmission.

encryption See data encryption.entity A specific thing in a relational database about

which information is collected and stored.entity-relationship diagram (ERD) A graphical

method of identifying the entities in a relationaldatabase and showing the relationships betweenthem.

environment Everything that influences or isinfluenced by an information system and itspurpose.

ergonomics The relationship between people andtheir work environment.

ethernet The first industry-standard local areanetwork access method, or protocol, based on a bustopology.

evaluation The process of determining whether thesystem is working as expected or whether changes are required.

expert system An information system that providesinformation and solves problems that wouldotherwise require a person experienced in thatfield (an expert).

expert system shell A ready-made expert systemthat contains no knowledge.

explanation mechanism A method of checking howa deduction was inferred in an expert system.

extranet An intranet that is accessible to customers,suppliers or others outside the organisation.

feasibility study A short report that analysespotential solutions and makes a recommendation.

fibre-optic cable A cable that uses a laser of light tocarry data in small glass fibres about the diameterof a human hair.

field A specific category of data in a database.field name The name of a field in a database.field size The number of characters allowed in a

field in a database.file A collection of information stored on a computer

system and given a name. A file in a database ismade up of records, fields and characters.

file server A controlling computer in a network thatstores the programs and data shared by users.

filter A tool to limit the records viewed in adatabase. A tool used to display only the desiredata in a spreadsheet.

Glossary

firewall A data protection method used on theInternet or any network to verify and authenticateall incoming data, including passwords.

flat file database A database that organises data intoa single table.

foreign key An attribute (field) of a table in arelational database that is a primary key in anothertable.

form An arrangement of fields on the screen, oftenfrom a single record, that is used to view, enter, andchange data in a database. Also a document used tocollect data from a person.

formula An instruction to perform a calculation in aspreadsheet.

forward chaining An inference strategy in whichthe user supplies all the data before the question isasked or the inference is made.

frame buffer A section of memory that stores theimage currently being displayed.

frame grabber A tool used to capture and digitiseimages from a video.

frame rate The speed of a video or animation,measured in frames per second.

full-duplex mode The transmission of data in bothdirections at the same time.

function A predefined set of operations in aspreadsheet that perform simple or complexcalculations.

fuzzy logic A term used to describe the variablesthat exist between a ‘true’ and a ‘false’ situation inan expert system or neural network.

Gantt chart A bar chart with each bar representinga task or stage in the system development cycle. Itprovides a quick method of determining whetherthe project is on schedule.

gateway A combination of hardware and softwareused to link two different types of networks.

grandfather-father-son A backup procedure thatrefers to at least three generations of backupmaster files.

graphic A picture, such as a drawing, painting, orphotograph.

group decision support system (GDSS) Aninformation system that assists users to make adecision by working together in a group.

half-duplex mode The transmission of data in bothdirections but not at the same time.

handshaking The sending of signals to reach anagreement about which protocol to use toaccomplish an exchange of information.

hard disk A disk made of metal or glass and coveredwith magnetic material. It is used to store data.

hardware flow control A handshaking method thatuses a dedicated connection, such as a wire, tocontrol the flow of data.

head-up display A device worn on the head todisplay information.

hierarchical database A database that organises datain a series of levels.

hypertext markup language (HTML) A set of

special instructions (called tags) that indicate howparts of a document on the Web will be displayedand navigated.

HTML editor A software program that specialisesin writing HTML code.

HTML tag An instruction in HTML.hub A central connecting device in a network. Data

arrives at the hub from one or more devices and isforwarded out using just one cable.

human-centred system A system that makesparticipants’ work as effective and satisfying aspossible.

hyperlink The highlighted item (usually anunderlined word or graphic) that allows anelectronic connection between documents in ahypertext system. Also called link or hotword.

hypermedia A combination of media whoselocations are linked to provide an easy way tonavigate between the documents.

hypertext A system that allows documents to becross-linked in such a way that the user can movefrom one document to another by clicking on alink.

image Data in the form of a picture, such as adrawing, painting or photograph.

implementation plan A document that details theparticipant training, method of conversion andtesting for a new information system.

indexed access Direct access that involves the useof an index.

inference engine A set of routines in an expertsystem that carries out deductive reasoning byapplying the facts, assumptions, theories, and rulesin the knowledge base.

information Data that has been ordered and givensome meaning by people.

information kiosk A multimedia device that allowspeople to use a touch screen and select informationabout an organisation or service.

information processes The steps taken to changedata into information: collecting, organising,analysing, storing/retrieving, processing,transmitting/receiving and displaying.

information processing The creation of informationby processing data using information technology.

information system A set of information processesrequiring participants, data/information andinformation technology. It is created for a purposeand to operate in a particular environment. Itperforms the seven information processes.

information technology The hardware and softwareused by an information system.

intelligent agent A piece of software used to searchthrough relational databases for relevant data.

intelligent system A system that receives data fromthe environment, reacts to that data and producesan intelligent response.

interactivity The property of an information systemthat allows the user to choose the sequence andcontent of the information to be displayed.

263

264 Glossary

Internet A global collection of computer networksthat speak the same language and are hookedtogether to share information.

intranet A private network that uses a similarinterface to the Web.

key A field in a database that is used to sort andretrieve information.

knowledge base A set of general facts and if-thenrules supplied by an expert and forming part of anexpert system.

knowledge engineer A person who builds an expertsystem.

label Text entered into a cell of a spreadsheet toprovide some explanation of the spreadsheet.

link See hyperlink.liquid crystal display (LCD) A display device that

consists of a flat screen formed from a layer of liquidcrystal material placed between two polarising sheets.

local area network (LAN) A network that connectscomputers (or terminals) within a building orgroup of buildings on one site.

logical operator A series of characters or a symbolused to combine simple queries.

logon The procedure used to get access to thenetwork.

lossless compression A type of compression thatworks by replacing repeated data with somethingthat takes up less room.

lossy compression A type of compression thatremoves a number of data bytes from the file.

machine-centred system A system designed tosimplify what the computer must do at theexpense of participants.

macro A series of commands stored in a file thatcan be executed by pressing a few keys.

magnetic disk A circular piece of metal or plasticwhose surface has been coated with a thin layer ofmagnetic material. It is used to store data.

magnetic tape A very long, thin strip of plastic,coated with a thin layer of magnetic material. It isused to store data.

mail server A computer in a network that providesemail facilities.

maintenance The modification of the system bymaking minor improvements.

management information system (MIS) Aninformation system that provides information forthe organisation’s managers. It presents basic factsabout the performance of the organisation.

manufacturing The process of producing a productthat meets a specific need.

mass production The manufacture of products inlarge quantities by standardised mechanicalprocesses.

messaging system A system used to send messagesto people in different locations who can receive themessage at a different time.

metadata Information about data.magnetic ink character recognition (MICR)

Characters written using magnetic ink that

contains magnetised particles. It is widely used bybanks to print serial numbers on cheques.

microwave A high frequency radio signal sentthrough space in a straight line from one antennato another.

model A representation of some aspect of the realworld.

modem A device that enables the transmission ofdata from one computer to another.

morphing Animation technique that involves the smooth change between two different images.

multimedia The presentation of information usingtext, graphics, animation, audio and video.

multimedia system An information system thatcombines different types of media.

MYCIN A famous expert system designed to assistnon-specialist doctors in the diagnosis andtreatment of bacterial blood infections.

network A number of computers and theirperipheral devices connected together in some way.

network administrator A person who manages anetwork within an organisation.

network database A database that organises data asa series of nodes linked by branches.

network interface card (NIC) An expansion cardthat fits into an expansion slot of a computer orother device, so that the device can be connectedto a network.

network licence A licence that allows people to usea program on a network.

network operating system (NOS) An operatingsystem that is designed primarily to supportcomputers connected on a LAN.

network topology The physical arrangement of thedevices on a network.

neural network An information system that workslike the human brain and is capable of learning.

newsgroup A discussion group where people canread messages and join in discussions by sending orposting messages.

node A device in a network.noise Unwanted data or interference that reduces

the quality of a signal.normalisation The process of organising data into

tables so that the results of using the database areunambiguous and as intended.

number A data type consisting of predefinedcharacters (usually numbers) whose meaning andformat are specified.

numerical control (NC) A form of programmableautomation in which numbers control a machine.

office automation system An information systemthat provides people with effective ways tocomplete administrative tasks in an organisation.

offline storage The use of a peripheral device that isnot under the user’s direct control to store data.

online storage The use of a peripheral device that isunder the user’s direct control to store data.

Glossary

operation manual A document containing detailedprocedures for participants to follow when using anew system.

optical disc A polycarbonate plastic disk the surfaceof which is covered with a reflective layer of metal.It is used to store data.

organising The information process that involvesthe modification of data by arranging, representingand formatting.

overdamping Damping that occurs if the change istoo slow and the actuator takes longer to reach thedesired level or position.

ownership See data ownership.packet switching A data transmission technique

that divides messages into small data packets,transmits the packets and later joins the packets toform the original message.

parallel conversion Conversion to a new systeminvolving the old and the new system both workingtogether at the same time.

parallel transmission The transmission of datasimultaneously using separate channels.

parameter A variable that is given a constant valuefor a particular application.

parity bit An additional bit attached to the binarycode for each transmitted character whose purposeis to check the accuracy of the received character.

parity checking A method of checking for errors indata transmission using an additional bit called aparity bit.

partial backup A backup that only stores parts ofthe master file.

participant A person who carries out theinformation processes within an informationsystem.

participant development The development of aninformation system by the people who will use it.

path-based animation Animation that involvesdisplaying the movement of objects onto a fixedbackground in a particular sequence or path.

phased conversion Conversion to a new system bygradually implementing the new system.

pilot conversion Conversion to a new system bytrialing the new system in a small portion of theorganisation.

pivot table An interactive table in a spreadsheetthat quickly summarises large amounts of data.

pixel The smallest part of the screen that can becontrolled by the computer.

port A socket used to connect peripheral devices.preliminary investigation The process of

determining whether a quick fix of the existingsystem will solve the problem or a new system isnecessary.

presentation software Software used to make aprofessional presentation to a group of people.

primary key A single key or compound key in adatabase that must have a value; i.e., it cannot beempty or null.

primary source Data collected first hand.

print server A computer in a network that controlsone or more printers and stores data to be printed.

privacy The ability of an individual to controlpersonal data.

processing The information process that involvesthe manipulation of data and information.

programmable logic controller (PLC) A computerthat performs the timing and sequencing functionsrequired to operate industrial equipment in anautomated manufacturing system.

programmer A person who converts a writtendescription of a problem into a set of computerprograms.

project leader A person who develops schedules,checks work and resolves conflicts for a projectteam. Also called project manager.

project management The process of planning,scheduling and controlling all the activities withineach stage of the system development cycle.

project plan A summary of a project that specifieswho, what, how and when.

protocol In data transmission, a set of rules thatgoverns the transfer of data between computerdevices.

prototype A working model of an informationsystem built in order to understand therequirements of the system.

query A search of a database for records that meet acertain condition.

query by example (QBE) A common method fordescribing a query. It requires the user to enter thecriteria against a field.

query language (QL) A specialised languagedesigned to allow users to search for informationfrom a database.

random access See direct access.range A group of cells in a single row or column or

in several adjacent rows and columns of aspreadsheet.

raster scan A device that fires an electron stream in aseries of zigzag lines to produce an image on ascreen.

real-time transaction processing A transactionprocessing method that processes dataimmediately.

record A collection of facts about one specific entryin a database.

refreshing The process of maintaining an image ona screen by repeating a raster scan.

relational database A database that organises datausing a series of related tables.

relational operator A character or a symbolindicating the relationship between twoexpressions in a query.

relationship The way entities are related to eachother in a relational database. Relationships can beone to one, one to many, and many to many.

relative referencing Copying a formula in which thecell references change so that they relate to thedestination.

265

266 Glossary

removable cartridge A hard disk encased in a metalor plastic cartridge that can be removed like afloppy disk. It is used for data storage.

repeater A device used during the transmission ofdata to rebuild a fading signal to its originalstrength and shape.

report A formatted and organised presentation of data.

requirement definition See preliminary investigation.requirement report A statement about the need for

a new system.resolution A measurement of the detail of an image

produced on a screen or output to a printer.response time The amount of time taken by the

computer to respond to a command.ring topology A network topology in which all

devices are attached so that the path is in the shapeof a continuous circle.

router A device that determines where to send adata packet between at least two networks.

sample size The number of bits per sample. Alsocalled bit resolution.

sampling The method used to digitise a soundwave.

sampling rate The number of times a sample (slice)is taken from the sound wave.

scanner An input device that can electronicallycapture text or images, such as photographs anddrawings.

schema An organised plan of the entire databaseshowing how and where the data is found,descriptions of the data and the data’s logicalrelationships.

schematic diagram A graphical tool to help define adatabase and develop a schema.

screen A display surface that provides immediatefeedback about what the computer is doing.

search engine A database of indexed Web sites thatallows a keyword search.

search robot A program that accesses Web sites andgathers information for search engine indexes.

searching The process of examining the database toretrieve data.

secondary key A field in a database that containsuseful items of data, not necessarily unique andoften used in searches.

secondary source Data that is collected or createdby someone else.

sensor An input device that measures data from theenvironment, such as temperature, pressure,motion, flow and light. Also called transducer.

sequential access A method of retrieving data thatsearches the storage medium from its beginningand reads all the data until it finds the desired data.

serial port A type of port that transmits data one bitat a time using only one communication line.

serial transmission The transmission of data oneafter the other.

server A computer that provides services to othercomputers on the network.

signal The physical form in which data istransmitted, such as pulses of electricity in a wireor pulses of light in a fibre-optic cable.

signal conditioning The modification of a signal fornormal usage.

simplex mode The transmission of data in onedirection only, from the sender to the receiver.

simulation The use of a model.single key A field in a database in which each item

of data is unique.software flow control A handshaking method that

uses a special code sent with the data to controlthe flow of data.

software package Application software bought tocover most requirements.

sorting The process of arranging data in a particularorder.

sound card An expansion card that transforms thesounds from a microphone into audio.

speaker A device used to produce sounds.spreadsheet A rectangular grid made up of rows

and columns to organise and store data thatrequires some type of calculation.

structured query language (SQL) A query languageused to access and manipulate data in a relationaldatabase.

star topology A network topology that has a centralcomputer with each device connected directly to itbut not to one another.

storing and retrieving The information process thatinvolves saving data and information for later use(storing data) and obtaining data and informationthat has been previously saved (retrieving data).

storyboard A series of frames, each representing adifferent action or screen image. It shows thenavigation between frames.

switch A device that directs data packets along apath.

synchronous transmission Serial transmissionmethod in which data is all sent at the same rate;i.e., the same number of bytes is sent each second.

system A group of elements that work together toachieve a purpose.

systems analyst A person who performs the analysisto decide whether a new or updated system willsolve the problem.

system development cycle A traditional method fordeveloping a new information system.

system flowchart A graphical method ofrepresenting both the flow of data and the logic of a system.

table In a document, rows and columns of cells thatare filled with text and graphics. In a database, theorganisation of data into columns (fields) and rows(records).

technical support staff People who assistparticipants of a system on an as-needed basis.

teleconferencing The use of an electronictransmission to allow a meeting to occur at thesame time in different locations.

Glossary

template A document created for repeated use.terminal A device used to send data to and receive

data from another computer system.test data A range of data values structured to test all

decisions made within an information system andto cover all possible combinations of data that maybe encountered.

text A data type consisting of letters, numbers andother characters whose meaning and format are notspecified.

titling The placement of a caption to accompany animage or graphic element.

token ring A local area network access method, orprotocol, based on a ring topology.

top-down design The process of dividing a large,complicated problem into a series of smaller, easierto solve problems.

topology See network topology.training specialist A person who teaches

participants how to operate their system.transaction An event that generates or modifies

data that is eventually stored in an informationsystem.

transaction processing monitor Software thatallows transaction processing application programsto run efficiently.

transaction processing system (TPS) Aninformation system that collects, stores, modifiesand retrieves the daily transactions of anorganisation.

transition A special effect used to change from oneimage or screen to another.

transmitting and receiving The information processthat involves the transfer of data and informationwithin and between information systems.

tuple A row in a table of a relational database.tweening The process of taking two images of an

animation and producing intermediate images sothat the animation is smoother.

twisted-pair A cable that consists of two thininsulated copper wires, twisted to form a spiral.

underdamping Damping that occurs if the changeis too fast and the actuator overshoots the desiredlevel.

uploading The action of transferring a file from theuser’s computer to another computer.

uniform resource locator (URL) The address of afile or resource on the Web.

user-friendly A term used to describe a tool thatpeople find easy to use.

value A number stored in a spreadsheet on whichcalculations are carried out.

vector display system A special type of cathode raytube display that only displays vector graphics. Itdirects the electronic stream to draw only the linesrequired for the image.

vector graphic A graphic made up of objects, suchas a straight line, curve, or shape.

video A data type that combines pictures andsounds displayed over time.

video conference A meeting that allows people atdifferent locations to see video images of eachother on a screen, as well as to hear speech.

virtual reality The use of computer modelling andsimulation to enable a person to interact with anartificial environment.

voice mail (v-mail) A messaging system that allowscommunication with other people by storing andforwarding spoken messages.

wide area network (WAN) A network thatconnects computers (or terminals) over hundredsor thousands of kilometres.

warping An animation technique that involvestransforming or distorting a portion of an image.

World Wide Web (Web or WWW) Part of theInternet and the most user-friendly way to accessthe Internet.

Web browser A software program stored on acomputer that allows access to the Web.

Web page A single document on a Web site, usuallyin HTML format.

Web server A computer in a network that providesa connection to the Internet.

Web site A linked collection of Web pages by thesame organisation or person.

‘what if’ The process of making changes to the datain a spreadsheet and observing the effects of thosechanges.

wildcard character A character that represents oneor more unknown characters in a search or query.

workstation An intelligent terminal, such aspersonal computer, in a network.

267

268 Index

absolute referencing 162–3acceleration sensors 201accuracy of data 69, 141–2active listening 6actuators 188, 209–10AIFF (Audio Interchange File Format) 252aliasing 221analog data 100analog-to-digital conversion 204–5, 224

see also digital-to-analog conversionanalysis report 17Animated GIF (Graphics Interchange Format) 252animation 221, 236

cell-based 227file formats 252path-based 227processing 227–8software 243

application software, multimedia 241–2ASCII 250assembly line production 192–3asymmetric encryption 55asynchronous transmission 87, 88attachments, email 102attribute 44audio 221, 236

conference 81file formats 251–2software 242storage 224–6

authoring software, multimedia 242–3automated manufacturing systemsassembly line production 192–3automated warehouses 193

CAD/CAM 193–4characteristics 187–91data collection 198–205human-centred systems 214and information display 208–11mail sorting 195reliability and quality 214–15safety 215semi-automation 214and work 213

automated warehouses 193automatic teller machine (ATM) 135automation

defined 187of jobs 139–40reasons for 195–6

backup 56, 128–31backward chaining 168–9banking

and decision support systems 152Internet 106–7

bandwidth 77bar charts 174

barcode readers 135, 202–4baseband transmission 95batch transaction processing 114–15, 116–17,

124–5, 130–1see also real-time transaction processing

baud rate 78bias 141bill generation 124bit

depth 223mapping 223

bit-mapped graphics 221file formats 250-–1

bits data 79stop/start 79

bits per second (bps) 78, 79block diagram 190–1BMP (Bit-map) 250bridges 93–4broadband transmission 95bus topology 92

CAD/CAM 193–4, 198–9cameras 246car industry 192–3CD-ROM speed 234cell 221cell-based animation 227censorship 106CGM (Computer Graphics Metafile) 251characters 43, 236charge-coupled devices (CCD) 202charts 156, 173–4check digit 69cheque clearance 124checksum 78CIM (computer-integrated manufacturing) 199client-server architecture 102coaxial cable 95CODEC (coder-decoder) 249collecting data 100, 134–7, 176–8, 188,

198–205, 245–7colour graphics 223column charts 174communication

concepts 87–98skills 6settings 79systems 76–86, 104–8

composite key 44video system 246

compression 248–9ratio 249techniques 249–50

computer games 230

Index

Index

operators 30computer-based training (CBT) 230confidentiality 104conflict resolution 6constraints 15content provider 228context diagrams 20–1controller 188conversion method 27–8copyright 254–5credit cards 125cross fade 238CRT displays 238CSMA/CD 92cyclic redundancy check (CRC) 78

damping devices 205data

access to 70–1accuracy 69, 141–2analog 100analysing 137–8bits 79collection 100, 134–7, 176–8, 188, 198–205digital 101–2extracting summary 172filtering 172flow 88identification 176–7importance of 141–2integration of 248integrity 70, 142, 256–7management 148, 149matching 175methods of accessing 54modelling 47–9ownership of 71processing 100–2, 188, 207–8range 176redundancy 48security 56, 141storage and retrieval 53–62, 126–33, 178structured 176transmission 87–98, 211–12type 47unstructured 176, 180validation 69, 117

data dictionary, 23, 47–8Data Encryption Standard (DES) 56data flow diagram (DFD) 21–2data mart 156data mining 71, 138, 171–2, 180–1data projection panel 239data projectors 239–40data sources 69, 76, 160

primary 176secondary 176

data warehouse 71, 127–8, 156database information systems 38–9database of facts 167database management systems (DBMS) 53–4, 55

56

databases constructing different views 65–6distributed 54–5defined 126, 156, 175and files 126–7flat file 43–4relational 44–7

decisionmaking 15–18, 180, 182tables 22–3trees 22–3

decision support systems (DSSs) 37, 137–8and analysing 171–5characteristics of 147–51issues related to 179–82nature of 147–9and organisation 159–65and processing 167–70semi-structured situations 149–50, 152–3structured situations 149types of 154–8unstructured situations 150–1, 153, 180

decoding 100–2decompression 248–9delta information 239design

multimedia 235–6principles 235–6social and ethical 8–12solutions 18–25specifications 17of systems 8–9tools 20–5

dialogue management 148, 149digital

cameras 246data 101–2television 256

digital-to-analog conversion 210–11, 224see also analog-to-digital conversion

digitising 256methods for 245–8

direct access 54conversion 27users 188–9directories 61

displaying 64, 102–3in multimedia systems 238–44

distributed databases 54–5domain/key normal form (DKNF) 49DVD 234–5

economic feasibility 16education and multimedia 230EFTPOS 85, 103electric motors 209electronic banking 85–6electronic commerce (e-commerce) 85electronic junk mail 104electronic mail (email) 82–4employment and automation 139–40, 213

see also work

269

270 Index

encoding 100–2encryption 55–6entertainment and multimedia 230entity 44entity-relationship diagram (ERD) 48environment 10–11EPS (Encapsulated Postscript) 251equity 11–12ergonomics 9–10erroneous inferences 181error checking 78ethernet 92ethical design 8–12ethics 10evaluation, system 30expert knowledge 180expert systems 37, 156–7, 167–8, 175, 177

shells 164explanation mechanism 168extranet 98

fax 81–2feasibility study 15–16fibre-optic cable 95field 43

name 47size 47

file 43formats 250–2

filters data 172noise 211

firewall 56First Norm Form (1NF) 49flat file databases 43–4flight simulators 233flow

control 79sensors 201

flowcharts, system 24–5foreign key 46forms

on-screen 46, 136–7paper 135Web 137

formulas 155, 161–4forward chaining 168, 169frame

buffer 223grabber 246–7rate 226

full-duplex mode 88functions, spreadsheet 162–3furniture 9fuzzy logic 169–70

Gantt chart 5gateways 93–4gender equity 11–12geographic information system (GIS) 153–4ghost site 70GIF (Graphics Interchange Format) 250–1grandfather-father-son backup procedure 130

graphics colour 223file formats 250–1software 242

group decision support system (GDSS) 181–2

half-duplex mode 88handshaking 77, 88–9hard disk 55hardware

data collection 134–5flow control 77and multimedia systems 223–8, 238–40network 92–6

head-up displays 240health and safety 9–10heuristic rules 177HTML 51–2, 250

editors 243–4hubs 94human-centred systems 8, 214hydraulic pump 210hyperlink 49, 220hypermedia 49, 60–2, 249hypertext 49, 220

identification of data 176–7image storage 223–4images 221, 236implementation 26–8index 54, 60indexed access 54inference engine 167–9information

kiosks 232management software 4and multimedia 231–2processes 36, 64–7, 100–3, 134–8, 176–8,207–12, 245–53

information systems 36–9characteristics 36database 38–9types and purposes 37–8

intelligent agents 171, 178systems 179–80

interactive environment 233interactivity 147, 222Internet 105–7

appropriate use of 255banking 106–7and censorship 106radio and video 107trading 105

Internet Industry Association (IIA) 106interview techniques 6intranet 98inventory tracking 202–4

jobs see employmentjournal 129JPEG (Joint Photographic Experts Group) 250

Index

keys 43–4knowledge

base 164–5, 167engineers 177expert 180

label 154LCDs (liquid crystal displays) 239leisure and multimedia 230library loan system 123light sensors 201–2line charts 174linear regression models 173link see hyperlinklist check 69live video 255local area networks (LANs) 90, 92, 95

wireless 96logical operators

in queries 59in spreadsheets 162–3

logon and logoff procedures 97–8

machine-centred systems 8, 214macros 156, 170magnetic ink character recognition (MICR)

134–5magnetic tape 55, 130mail sorting 195maintenance, system 30–1management

data 148, 149dialogue 148, 149model 148, 149

management information systems (MISs) 38, 138managers 30manual transaction systems 118manufacturing 187mass production 207media

and multimedia design 236types of 220–2

merging technologies 255–6messaging systems 81–6, 104metadata 47microphones 247microwave transmission 95–6MIDI (Musical Instrument Digital Interface) 252mobile phones 96model management 148, 149mono 224morphing 227motion sensors 201MPEG (Motion Picture Expert Group) 252MP3 (MPEG Audio Layer 3) 252multimedia systems

animation processing 227–8audio storage 224–6characteristics 220–8defined 220design 235–6displaying in 238–44education and training 230

encyclopaedia 231examples 230–6hardware 238–40image storage 223–4and information 231–2and interactivity 222leisure and entertainment 230major areas of use 230–3and mode of display 222and people 228and print 222and technology advances 233–5and text 220, 236video processing 226–7virtual reality and simulations 232–3

negotiation skills 6network

access methods 92administrator 96hardware 92–6software 96–8topologies 91–2

network interface card (NIC) 93network operating systems (NOS) 96–7networks 89–91

local area (LANs) 90, 92, 95, 96neural 157–8, 175wide area (WANs) 90

neural networks 157–8, 175node 49, 89noise 211non-computer

organisational methods 42–3procedures 140

normalisation 48–9numbers 220–1numerical control (NC) 194

office automation systems 38offline storage 55online storage 55operating systems 96–7operation manual 31operators

in queries 58–9in spreadsheets 162–3

optical disc 55organisation methods 42–52organisational feasibility 16organising a multimedia product 247–8OSI reference model 77

packet switching 90parallel

conversion 27transmission 87

parameter 79parity 79

checking 78participant

development 18–20training 27

271

272 Index

passwords 97path-based animation 227people

in multimedia systems 228as participants 140

phased conversion 27photodiode 202PICT (Picture) 251pie charts 174pilot conversion 28pivot table 172pixel 221point-of-sale terminals 122presentation software 241presentations, on-screen 241primary

data 176key 44

print and interactivity 222and mode of display 222and multimedia 222

privacy 70, 104, 181, 255private leased line 90processing data 100–2, 188, 207–8, 248production

assembly line 192–3batch system 208continuous systems 208discrete system 208mass 107

programmable logic controllers (PLCs) 192programmers 6project

goal 4leader 6management 4management software 4, 242manager 228plan 4–5, 17

projection devices 239–40protocols 77, 88–9prototypes 13–14

query by example (QBE) 57query language 59querying 57QuickTime 252

radio and Internet 107range 154

check 69raster scan 239RealAudio file format 252real-time transaction processing 115–17, 120–3,

132–3see also batch transaction processing

receiver 76record 43recovery process 129refreshing 239relational

databases 44–6

operators 58relationship 44relative referencing 163–4relay 210removable cartridge 55reporting 64–5reports 172

analysis report 17requirement 13

requirement report 13reservation systems 120–1resistance thermometers 200resolution 221retrieval, data 53–62, 126–33, 178, 249–53RTF (Rich Text Format) 250ring topology 92routers 93

safety, workplace 215sample size 224sampling rate 224satellites 96scanners 245schedule feasibility 16schema 44–6schematic diagrams 48screen 222, 238–9

layout 236script 247search

engines 60–2, 172robot 62

searching 57–62secondary

data 176key 44

security, data 56, 141–2semi-automation 214sensors 188, 199–202

flow 201light 201–2motion 201pressure 200–1temperature 200

sequential access 54, 130, 131serial transmission 87, 88servers 93shielding 211signal 211signal conditioning 211simplex mode 88simulations 232–3simulators, flight 233single key 44skills

communication 6negotiation 6

social design 8–12software animation 243

application 241–2audio 242authoring 242flow control 77

Index

graphics 242information management 4multimedia 240–4network 96–8presentation 241project management 4, 242video 242

solenoids 209solutions, designing 18–25sorting 56–7sound card 247speakers 222, 240speed of transmission 77–8spreadsheets

analysis 172–4defined 154–6designing 160–4functions operators 162

SQL 59–60star topology 91statistical analysis 173stepper motors 209–10stereo 224stock prices 153storage

data 53–62, 126–33, 178, 249–53media 55offline 55online 55

storyboard 50–1, 247–8structured data 176Structured Query Language (SQL) 59–60switches 93symmetric encryption 55synchronous transmission 87, 88system

defined 190designer 228evaluation 30flowcharts 24–5maintenance 31testing 28, 30

system development cycle 3, 30systems

analysts 6automated manufacturing 187–95, 198–205,

208–11, 213–15communication 76–86, 104–8and ethics 10–12expert 37, 156–7, 167–8, 175, 177human-centred 8intelligent 179–80machine-centred 8messaging 81–6, 104multimedia 220–8, 230–6, 238–43, 245–57reservation 120–1transaction processing 37, 113–18, 119–25,

130–1, 134, 139–42 see also decision support systems

tables 46team building 6

technicalfeasibility 16staff 228support staff 27

technologies, merging 255–6telecommuting 107teleconferencing 81telephone 81, 103temperature sensors 200templates 155, 160terminals 89test data 28testing, system 28text

colour 236file formats 250and multimedia 220, 236

thermistor 200thermocouples 200TIFF (Tagged Image File Format) 251titling 236token ring 92top-down design 18touch screens 239training and multimedia 230transaction processing monitor (TP monitor) 116transaction processing systems (TPSs) 37, 113–18,

119–25, 130–4, 139–42transducers 199transition 241transmission

of data 87–98, 211–12media 76, 94–6microwave 95–6speed 77–8wire 94–5wireless 95

transmitter 76tuple 46TWAIN (Technology Without An Interesting

Name) 245tweening 227twisted-pair cable 95two-phase commit 55type check 69

uniform resource locator (URL) 49–50unstructured data 176, 180user interface 161user-friendly 8–9

validation of data 69, 117VCR (video cassette recorder) 246vector

display systems 239graphics 221

video 236cameras 246capture 226capture card 246conference 81defined 222file formats 252

273

274 Index

and Internet 107live 255processing 226–7software 242

virtual reality (VR) 232–3voice mail 82

warping 228WAV file format 251Web

browsers 243site 233

what-if models 154, 172–3wide area networks (WANs) 90wildcard characters 58wire transmission 94–5WMF (Windows Metafile Format) 251work

environment 9–10nature of 10, 139–40, 213

working from home 107–8workplace safety 215workstations 90World Wide Web (WWW) 49, 233–4

Acknowledgments

The publisher wishes to thank Catherine Webber, Rick Walker and Anthony Connolly for their assistancewith this project.

The author and publisher would like to thank the following for granting permission to reproduce thecopyright material in this book:

The Age, pp. 246 (bottom), 252; Coo-ee Picture Library, p. 96; Corbis/Australian Picture Library, p. 117;Malcolm Cross, pp. 28, 76, 77, 130, 177, 234, 240, 247; Randy Glasbergen, p. 102; Great SouthernStock/Brian Gilkes, p. 123, 150 (centre); The Image Bank, p. 193; Mark Parisi, pp. 31, 56, 141, 182, 195,232; PhotoDisc, pp. 7, 17, 27, 30, 38, 42, 81, 90, 107, 135, 140, 148 (all), 150 (right and left), 152, 160,199, 202; Redflex Systems, p. 232 (top); Ellen Sheerin, pp. 227, 228; Yurikamome, p. 179.

Every effort has been made to trace and acknowledge copyright. The author and publisher wouldwelcome any information from people who believe they own copyright to material in this book.

G.K. Powers

H e i n e m a n n

Information Processesand TechnologyInformation Processesand Technology

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ISBN 0-86462-512-X

780864 625120

You can visit the Heinemann World Wide Web site at

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HSC COURSE

Heinemann Information Processes and Technology:HSC Course has been written to meet all of the

requirements of the new Information Processes and

Technology syllabus in NSW. This text will help students to

develop their understanding of information processes in the

context of different information systems. It is designed to

build on the knowledge and skills gained in the Preliminary

course and to help students become confident, competent,

discriminating and ethical users of information technology.

This text provides up-to-date information, a practical

approach, and a large number of questions that cater for a

wide range of students.

Key features• list of outcomes and overview at the beginning of

each chapter

• social and ethical issues and Internet activities integrated

throughout the book

• numerous practical tasks that can be used with any

software or make of computer

• case studies and examples of information systems

• learning activities to help students apply the content in

every section

• chapter review at the end of each chapter

• interesting IT facts and cartoons to promote class

discussion

• key terms highlighted for quick reference

• glossary

• index.

Additional resources to support and extend this book are

available at Heinemann’s World Wide Web site, hi.com.au.

These include a sample teaching program, assessment

advice and answers to exercises from the textbook.

About the authorGreg Powers is a head teacher with many years’ experience

in writing and implementing computing studies programs.

He is the author of several highly successful texts including

Computing Studies–An Introductory Course.

Also availableHeinemann Information Processes and Technology:

Preliminary Course

ISBN 0 86462 501 4

Hein

em

ann In

form

atio

n P

rocesses a

nd T

echnolo

gy: H

SC

Cours

eG

.K. P

owers

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