Chapter 11 2000 by Prentice Hall. 11-1 System Analysis and Design: Methodologies and Tools Uma...

2000 by Prentice Hall. 11-1

Chapter 11System

Analysisand Design:Methodologies

and Tools

Uma GuptaIntroduction to Information Systems


Learning Objectives

After studying this chapter, you will be able to:

Describe the systems development life cycle methodology and its limitations

Discuss the prototyping methodology Explain end-user computing and the reasons for its growth Outline situations in which companies should use off-the-

shelf packages Explain why outsourcing is a viable option for building

information systems Identify and discuss structured tools for system development


System Development Life Cycle (SDLC)

A methodology to develop information systems that consists of these phases; system definition, analysis, design and programming, testing and implementation, and maintenance.


Five Basic Components of a System

ControlFeedback

Input Process Output

Feedback

THE SYSTEM’S ENVIRONMENT


Five Phases of SDLC

System Definition Describes what is being built and why it is being

built– “What problems are we trying to solve?”– “What are the system’s objectives?”

System Analysis (three activities) Understand the Problem Feasibility Analysis Establishing Functional Requirements


Functional Requirements Provide Answers to the Following

Questions Who will use the system and for what purpose? What are the specific information needs and

expectations of the user? Who will provide system input? Who will receive system output? Who will monitor system performance? When should the system be delivered? When will the system be updated? What are the maintenance requirements? What are the training requirements for this system?


Five Phases of SDLC (cont.)

System Design and Programming (three activities) Identify the appropriate technology to

implement the system Involve users in the development process

from the beginning Provide detailed specifications and show

how these specifications help to meet system goals



System Development System programming is just one phase in the

system development life cycle; it is highly complex, time-consuming and may take years to complete

System Testing (three types) Unit testing System testing Acceptance testing



System Implementation There are four types of conversion or

implementation strategies– Parallel conversion– Direct cutover– Pilot study– Phased conversion

System Maintenance Maintenance makes up about half of the

information systems activity in most companies


Four Implementation Strategies

Strategy DescriptionParallelconversion

•Old and new system run in parallel until new system becomes reliable

•Costly but safe approach

•Best suited to critical applications

•Old system is replaced with new system

•Less costly but more risky than parallel approach

•Best suited to noncritical applications

Directcutover


Four Implementation Strategies (cont.)

Strategy DescriptionPilot study •One department or unit serves as a testing

ground

•Good for systems that are moderately critical

•New system is slowly phased into the operational environment

•Safe and conservative approach

•Well suited to critical systems

Phasedconversion


Prototyping

A development methodology that relies on prototypes, working or experimental models of a system. Also known as rapid application development.


Four Steps of Prototyping

Define the problem and identify system requirements

Build the initial prototypeUse the prototype to refine existing

requirementsRevise and enhance the prototype


Off-the-Shelf Software Packages

Used by companies that do not have the resources or the inclination to build every part of their systems

Well suited for noncritical applications such as word processing, financial analysis, inventory control, scheduling project management, and employee benefits


The Percentage of Businesses that Use Off-the-Shelf versus Custom-Built

SoftwareCommercial package with

minimum customization49%

N/A2%

Custom-built26%

Commercial package withextensive customization23%

Source: Computer Sciences Corp. CIO, June 1, 1997, p. 88.


Outsourcing

The process of relying on external experts to meet the in-house information needs of an organization.


Four Reasons Why Organizations Outsource

Strategic Focus

Economies of Scale

Market Forces

Technical Considerations


How Businesses Outsource IT Functions

Different IT Functions Outsourcing Percentages

PC desktops and networks 35%Hardware support 34%Application development 30%None 24%Systems operations 22%Systems maintenance 19%Other 19%Call center management 15%


Structured Tools

Tools and techniques used to develop a system that supports a top-down approach in which users study the system starting from the highest level of detail and move to the lowest.


Tools Used to Analyze and Design Systems

Context Diagram Graphically depicts the overall system that is being

built Data Flow Diagrams

Provides a closer look at each subsystem that makes up the system

The DFD shows three items– How data flow in the system (inputs and outputs)– The processes that convert input into output– Where the data are stored in the system (data stores)


Tools Used to Capture and Represent System Data

An entity relationship diagram (ERD) is a graphical depiction that identifies the entities of a system and their relationships.


Five Steps in Creating an ERD

Step One: Developers and users work together as a team to identify the different entities in the system.Step Two: Establish the nature and scope of the relationship between the different entities identified in the previous step. Are the relationships one-to-one (1-1), one-to-many (1-M), or many-to-many (M-M)?Step Three: Describe each entity using a set of data elementsStep Four: Graphically depict the data associated with each entity and the type of relationship between different entities.Step Five: Check that no entity is missing and that the relationships between different entities are accurately portrayed.


Tools Used to Capture and Represent Processes

Structured programming is a tool that shows the processes that convert data into information.


Tools Used to Capture and Represent Processes (cont.)

A structure chart is a graphical systems tool that show the hierarchy of software modules and the relationship among different modules.



A system flowchart is a chart that shows how data flows in an information system. It also shows the processes, the sequence of the processes, relationships between the processes, and the data required for each process.



Decision tables are rules that capture the logic in system processes using a set of conditions (IF clauses) and actions (THEN clauses) shown in the form of a table.



A decision tree is a graphical representation of steps used to solve a problem.


Tools Used to Convert Program Specifications into Code

Structured english (pseudocode) is a code that converts program specifications written in English sentences into simple, easy-to-understand English phrases.


Business Guidelines for System Development Success

Every Information System Is a Business System Many IS projects fail because organizations view

them as technology projects, not business projects The Business of IS Departments Is Change

As the environment around the system changes, the system must adapt

Systems Development Is a Venture, Not and End in Itself


Business Guidelines for System Development Success (cont.)

One Size Doesn’t Fit All—Especially in a Global Environment Running into political, cultural, and technical glitches

in global system implementation is very common Build the Development Team

IS managers must build a culture that fosters creativity, innovation, and teamwork

It’s All about Users What really lies behind a successful system is not just

hardware and software but more important, people

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Chapter 11 2000 by Prentice Hall. 11-1 System Analysis and Design: Methodologies and Tools Uma...

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