apsi 02 isad isandse reviews ia earlydiscussion

8/16/2019 APSI 02 ISAD ISandSE Reviews IA EarlyDiscussion

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INFORMATION SYSTEMSANALYSIS AND DESIGN

Reviews of IS and Software Process



Principles of Reviews

! Systems concept

! Computer-based IS and software intensivesystems

! Analysis and design in the development ofabove systems



What is a System?

! A set of interrelated components

! With a clearly defined boundary

! Working together

! To achieve a common set of objectives

! By accepting inputs and producing output

! In an organized transformation process

! (O’Brien and Marakas, 2008)



Basic Functions of a System

! Input

!Capturing and assembling elements that enterthe system to be processed

! Processing! Transformation process that converts input into

output

!

Output! Transferring transformed elements to their

ultimate destination



Cybernetic System

! All systems have input, processing, andoutput

! A cybernetic system, a self-monitoring, self-

regulating system, adds feedback andcontrol:! Feedback is data about the performance of a

system

!Control involves monitoring and evaluatingfeedback to determine whether a system ismoving toward the achievement of its goal



A Cybernetic System



A Business as a System

!



Other System Characteristics

! If a system is one of the components of alarger system, it is a subsystem

! The larger system is an environment

! Several systems may share the sameenvironment

! Some may be connected via a shared

boundary, or interface



Components of an IS

! O’Brien and Marakas (2008)



Information System Resources

! People Resources

! Specialists

! End users

! Hardware Resources

!Machines

!Media

! Software Resources!Programs

!Procedures



Information System Resources

! Data Resources

! Product descriptions, customer records, employeefiles, inventory databases

! Network Resources! Communications media, communications

processors, network access and control software

! Information Resources

! Management reports and business documentsusing text and graphics displays, audio responses,and paper forms



Data Versus Information

! Data are raw facts about physicalphenomena or business transactions

! Information is data that has been converted

into meaningful and useful context for endusers

! Examples:

! Sales data is names, quantities, and dollar

amounts! Sales information is amount of sales by

product type, sales territory, or salesperson



IS Activities

! Input of data resources

! Data entry activities

! Processing of data into information

!

Calculations, comparisons, sorting, and so on! Output of information products

! Messages, reports, forms, graphic images

! Storage of data resources

! Data elements and databases! Control of system performance

! Monitoring and evaluating feedback



Our Focus

! Computer-based information systems

! Software-intensive systems

! Analysis and design in the development ofabove systems



Software

! What is it?



Software

! The concept of software resources includesall sets of information processinginstructions.

! This generic concept of software includesnot only the sets of operating instructionscalled programs, which direct and controlcomputer hardware, but also the sets of

information processing instructions calledprocedures that people need. (O’Brien andMarakas, 2008)



Software

! Computer programs and associateddocumentation. Software products may bedeveloped for a particular customer or may

be developed for a general market.(Sommerville, 2010)



Software products

! Generic products! Stand-alone systems that are marketed and sold to

any customer who wishes to buy them.! Examples – PC software such as graphics

programs, project management tools; CADsoftware; software for specific markets such asappointments systems for dentists.

! Customized products! Software that is commissioned by a specific

customer to meet their own needs.! Examples – embedded control systems, air traffic

control software, traffic monitoring systems.



Product specification

! Generic products

! The specification of what the software shoulddo is owned by the software developer and

decisions on software change are made by thedeveloper.

! Customized products

! The specification of what the software should

do is owned by the customer for the softwareand they make decisions on software changesthat are required.



Questions?20



The software process

! A structured set of activities required todevelop a software system.

! Many different software processes but allinvolve:

! Specification – defining what the system shoulddo;

! Design and implementation – defining theorganization of the system and implementing thesystem;

! Validation – checking that it does what thecustomer wants;

! Evolution – changing the system in response tochanging customer needs.



Software process model

! A software process model is an abstractrepresentation of a process. It presents adescription of a process from some

particular perspective.



Software process descriptions

! When we describe and discuss processes, weusually talk about the activities in theseprocesses such as specifying a data model,designing a user interface, etc. and the

ordering of these activities.! Process descriptions may also include:! Products, which are the outcomes of a process

activity;! Roles, which reflect the responsibilities of the

people involved in the process;! Pre- and post-conditions, which are statements

that are true before and after a process activity hasbeen enacted or a product produced.



Plan-driven and agile processes

! Plan-driven processes are processes where all

of the process activities are planned in advanceand progress is measured against this plan.

! In agile processes, planning is incremental andit is easier to change the process to reflectchanging customer requirements.

! In practice, most practical processes include

elements of both plan-driven and agileapproaches.

! There are no right or wrong software processes.



Software process models

! The waterfall model! Plan-driven model. Separate and distinct phases of

specification and development.

! Incremental development

! Specification, development and validation areinterleaved. May be plan-driven or agile.

! Reuse-oriented software engineering! The system is assembled from existing

components. May be plan-driven or agile.

! In practice, most large systems are developedusing a process that incorporates elementsfrom all of these models.



The waterfall model

apsi 02 isad isandse reviews ia earlydiscussion

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