information systems development itsc 1401, intro to computers instructor: glenda h. easter

Information Systems Information Systems DevelopmentDevelopment

ITSC 1401, Intro to Computers

Instructor: Glenda H. Easter

Information Systems Development, Chp. 11

ObjectivesObjectives Explain the phases in the system

development life cycle Identify the guidelines for system

development Discuss the importance of project

management, feasibility assessment, data and information gathering techniques and documentation

ObjectivesObjectives Describe how structured tools such as

entity-relationship diagrams and data flow diagrams are used in analysis and design

Differentiate between packaged software and custom software

Identify program development as part of the system development life cycle

ObjectivesObjectives Discuss techniques used to convert to a

new system and support an information system

A Few Terms, If You Please!A Few Terms, If You Please! A system is an organized way to

accomplish one or more goals. The system model describes the sequence

of input, processing, output, and storage. Computer systems that support businesses

are called information systems. The people who design systems are called

system analysts.

System Analysis and DesignSystem Analysis and Design Systems should be established using a step-

system, program-solving process known as system analysis and design.

This is also known as the system life cycle.

Systems Analysis The study of an activity, a procedure, or an

entire business Systems Design

The act of planning the technical aspects of the new system

Analysis and DesignAnalysis and Design

System Development System Development Life CycleLife Cycle

Preliminary Investigation Analysis Design/ Development

ImplementationSupport (Maintenance and Documentation)

Five Phases of the Systems Five Phases of the Systems Development Life Cycle: (SDLC)Development Life Cycle: (SDLC)

PreliminaryInvestigation:Needs Analysis

Systems Design Development Implementation Maintenance

What Is The System What Is The System Development Life Cycle?Development Life Cycle?

Organized set of activities used to guide those involved through the development of an information system

System Analysis and DesignSystem Analysis and Design Systems should be established using a step-

system, program-solving process known as system analysis and design.

This is also known as the system life cycle.

The System Life CycleThe System Life Cycle

Who Participates in the System Who Participates in the System Development Life Cycle?Development Life Cycle? Who participates in the system

development life cycle? Project team

Users Information systems personnel

Systems analyst Programmers

Steering committee

Who Participates in the System Who Participates in the System Development Life Cycle?Development Life Cycle?

The Cycle Requires Project The Cycle Requires Project Management ToolsManagement Tools Project management

Scope Project plan Gantt chart Deliverables

Project Management ToolsProject Management Tools

Data and Information Data and Information Gathering TechniquesGathering Techniques

How Is Data Collected?How Is Data Collected? Data is gathered through . . .

Observation Interviews Studying documents that describe the formal

lines of authority in the organization, and its standard operating procedures.

Reviewing the organizational chart and the levels of management and formal lines of authority.

Systems analysts spend much ofSystems analysts spend much oftheir time interviewing userstheir time interviewing users

What Initiates the System What Initiates the System Development Life Cycle?Development Life Cycle? External reasons Internal reasons Project requests

Why Make Changes to an Why Make Changes to an Information System?Information System? Organizations may experience organizational

growth. There may be a merger or acquisition. There may be new marketing opportunities. Governmental regulations make be revised. Availability of new technology may require

changes.

Phase 1: Preliminary Phase 1: Preliminary InvestigationInvestigation

Define the Problem - what do we have and what do we need?

Suggest alternative systems - develop a possible plan.

Prepare a short report summarizing results of preliminary investigation and suggesting alternative systems.

Determine the feasibility - Is there technology available to solve the problem?

Cost/Benefit Analysis

Identifying the Problem & Identifying the Problem & OpportunitiesOpportunities

To determine the problem, the system analyst talks to as many users as possible to discover what they do, when they do it, how they do it, and why. The analyst then recommends new system features or a new system.

Preliminary InvestigationPreliminary Investigation Analysis: Preliminary Investigation

Interviews Questionnaires Submit feasibility study to the steering

committee Recommend continue into the detailed

analysis phase

Selecting the Best SystemSelecting the Best System Will the system fit in with the organization’s

overall system? Will the system be flexible enough so it can

be modified in the future? Can it be made secure against unauthorized

use? Are the benefits worth the cost?

Phase 2: Phase 2: Analyzing & Documenting Analyzing & Documenting the Existing Systemthe Existing System

Analyze the existing system

Determine the new system’s requirements

Emphasis is on what the system should do

Phase 2: Analysis of the Phase 2: Analysis of the Current SystemCurrent System During this phase, data is collected about the

present system. The data is analyzed and new requirements

are determined. The data is summarized in documentation.

Analysis of the Current System Analysis of the Current System (Continued)(Continued) Detailed Analysis

Study the current system Identify the users’ wants, needs, and

requirements Present alternative solutions

Writing the System’s Design Writing the System’s Design Report for Upper ManagementReport for Upper Management Compare the cost versus the benefits. What is the effect of alternative designs on the

organization? Make recommendations for one of the

alternatives.

How Is Data Analyzed?How Is Data Analyzed? Data is analyzed to learn how information

currently flows in the present system. There are tools used to analyze this data. They

include: Checklists – Top-Down Analysis Grid Charts – Decision Tables System _ Automated Design

Flowcharts Tools

Analysis PhaseAnalysis Phase Structured Analysis and Design Tools

Entity-relationship diagrams (ERDs)

Analysis PhaseAnalysis Phase Structured analysis and design tools

Data flow diagrams (DFDs)

Tools Used During the Analysis Tools Used During the Analysis PhasePhase A Checklist is a list of questions focusing on

key issues of the present system.

Top-Down Analysis Methodology is similar

to an organizational chart which identifies the

top-level components of the system then

breaks the components down further into

smaller and smaller components for analysis.

Tools (Continued)Tools (Continued) Grid Charts - A data table showing

relationships between input and output documents. A checkmark at the intersection of a row and column would mean that the input document is used to create the output document.

System Flowcharts - shows the data or information flow into an information system.

Tools (Continued)Tools (Continued) Automated Design Tools also known as

Computer-Aided Software Engineering Tools (CASE) are software packages that evaluate hardware and software alternatives according to requirements given. CASE replaces line-by-line programming with a graphic and visual way to design programs.

Decision TablesDecision Tables A data table showing the decision rules

that apply when certain conditions occur.

Decision TreesDecision Trees

Structured or H ierarchy C harts

print reportheading

ca lcula tecom m iss ion

print sa lespersoncom m iss ion

process eachsepara tion

print tota lcom m iss ions

controlm odule

Program Design ToolsProgram Design Tools

Each box, or module, in a structure chart indicates a task that the program must accomplish

Program Design ToolsProgram Design ToolsCommission program

print headings

get first salesperson

calculate commission

print salesperson

get next salesperson

end of data

print total commission

AFlowchart

A flowchart is a diagram that shows the logic of a program. Each flowcharting symbol has a meaning

Data DictionaryData Dictionary

Analysis PhaseAnalysis Phase The Build-or-Buy Decision

System proposal Packaged software

Already developed software available for purchase

Custom software Application software developed by the user or at

the user’s request

Interviewing and ReportingInterviewing and Reporting User involvement in the new systems’ needs

assessment is critical because the system’s use may not be clear to analyst.

This stage is usually documented in a report for higher management so they can determine whether to continue with the project. The report would include: Current information system Requirements for new system A possible development schedule

Analysis PhaseAnalysis Phase Acquiring Necessary Hardware and

Software Identify technical specifications Solicit vendor proposals Test and evaluate vendor proposals Make a decision

Analysis PhaseAnalysis Phase Identifying Technical Specifications

Request for quotation (RFQ) Request for proposal (RFP) Request for information (RFI)

Phase 3: DesignPhase 3: Design The information obtained from users must be

converted into detailed technical requirements. The analyst does not make specific decisions

about which software to use for the system until the next stage.

System Design consists of three tasks: Designing the alternative systems Selecting the best system Writing the system’s design report

Designing Alternative SystemsDesigning Alternative Systems More than one design can be developed to meet the

needs. Each alternative systems would be evaluated for: Economic Feasibility (does cost justify the benefits?) Technical Feasibility (are reliable hardware, software

and training available to make the system work?) Operational Feasibility (Can the system be made to

operate in the organization?)

Design Phase (Database Design Phase (Database Design)Design) Detailed Design

Input and Output DesignInput and Output Design Mockup

Design Phase (Layout Chart)Design Phase (Layout Chart)

System FlowchartSystem Flowchart

PrototypingPrototyping Prototyping - This is an alternative to the six

phase process. It can be used to devise a model of a new system for users to try out if there is no time nor opportunity for evaluation, design, and testing.

Prototyping is a “quickie” way of building a system. Relying on prototyping alone can be risky because it could lead to changes being made without costs or other matters being considered.

PrototypingPrototyping Prototyping

Working model of the proposed system Rapid application development (RAD)

A A Prototyping Tool at Work

CASE (Computer-Aided CASE (Computer-Aided Software Engineering) ToolsSoftware Engineering) Tools CASE tools automate the design and

implementation of applications, as well as the procedures linking various applications.

Similar to OOP but differs because it is designed for high-level programming.

Redesigning can help you efficiently analyze an existing system.

Reengineering can help you find a better way of doing a job.

Case ToolsCase Tools

Phase 3: System DevelopmentPhase 3: System Development This stage involves the construction of the

actual system. When custom software must be designed, it is

created at this stage and is known as coding or writing the application in a programming language.

There are three steps involved during this phase. Developing the Software – Acquiring the Testing the New System Hardware

Stages of System DevelopmentStages of System Development Develop the Software

This may mean that you can purchase off-the-shelf packaged software that can be modified to suit operational needs.

You may have to custom design software when there is nothing on the market that will do exactly what you want done with a package.

Acquire Hardware Will the microcomputers easily communicate with

one another? Are the networks expandable? Will people have to undergo costly training?

Program Development Life Program Development Life Cycle (PDLC)Cycle (PDLC) Program development life cycle (PDLC)

Analyze the problems Design the programs Code the programs Test the programs Formalize the solution Maintain the programs

CodingCoding Coding

Programming in a specific programming language

Source Code: The program Structured Coding

Sequence Selection Looping

More About CodingMore About Coding Text Editors is an essential tool for coding. It

is similar to a word processor, but it is not as powerful and does not have many formatting features.

Structured Coding - This is the preferred technique in coding today.

Spaghetti Code - These were programs written in the late 1950s and early 1960s that were written in an individualistic style. It is very difficult to maintain this type of code.

Structured TechniquesStructured Techniques

Facilitates the creation of more reliable and easily maintained programs

Reduces program development time

Increases programmer productivity

Less testing and debugging

Programs simpler and easier to maintain

Correcting errors Debugger

a program to help identify errors

Can consume as much as 50 percent of the development time

DebuggingDebugging

Phase 4:Phase 4: Implementation Implementation PhasePhase Install and test the new system Train and educate users Convert to the new system

Testing and AcceptanceTesting and Acceptance

Alpha Testing Entering various kinds

of data In-house

Beta Testing Testing under actual

working conditions

TestingTesting Alpha Testing - Entering various data by

those creating the system. The data input is both correct and incorrect.

Beta Testing - Testing under actual working conditions prior to production. During this testing phase, the goal is to try to make the system fail in order to see how long it takes to recover.

Training and EducatingTraining and Educating Train and educate users

Classroom-style lectures One-on-one sessions User manuals

Train and Educate UsersTrain and Educate Users

Convert to the New SystemConvert to the New System Direct conversion (abrupt cut-over) Parallel conversion Phased conversion Pilot conversion Direct Data conversion

Four Types of ConversionsFour Types of Conversions Direct Approach - The old system is

abandoned and the new system is started.

This can be risky because the old system will

no longer be available to fall back on.

Parallel Approach - The old and new

systems operate side-by-side until the new one

has shown it is reliable. This is low-risk.

Four Types of ConversionFour Types of Conversions s (Continued)(Continued) Phased Approach - The new system is

implemented gradually over a period of time. This is the least risky approach, but it is also the most expensive.

Pilot Approach - The new system is tried out, first in one part of the organization, and then throughout the rest of the organization. It is less expensive than the parallel approach but somewhat riskier.

Various ConversionsVarious Conversions

Phase 5: Phase 5: Supporting the SystemSupporting the System

A post-implementation system review determines

whether the system has met its goals

In the final phase, the new system receives ongoing assistance to ensure that it has met its intended needs and works correctly

Phase 5: Support Phase 5: Support (Maintenance and (Maintenance and Documentation)Documentation) Ongoing -- 60+% of the work Updating

interim versions (1.3) correcting improving new versions (2.0)

Two Parts of System Two Parts of System MaintenanceMaintenance System Audit - The system’s performance is

compared to the original design specifications to determine if the new procedures are actually furthering productivity.

Periodical Evaluation - The new information system is periodically evaluated and further modified, if necessary.

Support PhaseSupport Phase Conduct post-implementation system

review Identify errors Identify enhancements Monitor performance

Documentation

This is the set of instructions that accompanies a system or application

Software documentation For programmers who maintain the program

User, Reference Documentation For people who use the program

Avoiding Mistakes User involvement is crucial A problem-solving approach works best Good project management skills are

needed Documentation is required Use checkpoints to make sure the

project’s on track Design for growth and change

information systems development itsc 1401, intro to computers instructor: glenda h. easter

information system slide

systems development

design systems

systems analysis

program development

system life cycle slide

computer systems

design slide

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