Introduction to Systems Analysis & Design

8/7/2019 Introduction to Systems Analysis & Design

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Introduction to SystemsIntroduction to Systems

Analysis & DesignAnalysis & Design

Structured System Analysis and DesignStructured System Analysis and Design



What is Systems Analysis and DesignWhat is Systems Analysis and Design

In business,In business, systems analysis and design systems analysis and design refers to therefers to the

process of examining a business situation withprocess of examining a business situation with

the intent of improving it through betterthe intent of improving it through betterprocedures and methods.procedures and methods.

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Ov erv iew of Systems Analysis andOv erv iew of Systems Analysis and

DesignDesign Systems development can generally be thoughtSystems development can generally be thought

of as having two major components: systemsof as having two major components: systems

analysis and systems design.analysis and systems design. S ystem design S ystem design is the process of planning a new is the process of planning a new

business system or one to replace orbusiness system or one to replace or

complement an existing system.complement an existing system.

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But before this planning can be done, we mustBut before this planning can be done, we must

thoroughly understand the old system and determinethoroughly understand the old system and determine

how computers can best be used (if at all) to make itshow computers can best be used (if at all) to make its

operation more effective.operation more effective.

S ystems analysis S ystems analysis , then, is the process of gathering and, then, is the process of gathering and

interpreting facts, diagnosing problems, and using theinterpreting facts, diagnosing problems, and using the

information to recommend improvements to theinformation to recommend improvements to the

system.system.

This is the job of the system analyst.This is the job of the system analyst.

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System analysts do more than solve current problems.System analysts do more than solve current problems.

They are frequently called upon to help handle theThey are frequently called upon to help handle theplanned expansion of a business.planned expansion of a business.

Working with managers and employees in theWorking with managers and employees in theorganization, system analysts recommend whichorganization, system analysts recommend whichalternative to adopt, based on such concerns as thealternative to adopt, based on such concerns as thesuitability of the solution to the particular organizationsuitability of the solution to the particular organization

and setting, as well as the employee support theand setting, as well as the employee support thesolution is likely to have.solution is likely to have.

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What Systems Analysis is NOTWhat Systems Analysis is NOT

It is NOT:It is NOT:

Studying a business to see which existing processesStudying a business to see which existing processes

should be handled by computer and which should beshould be handled by computer and which should be

done by nondone by non--computerized methods.computerized methods.

The emphasis is on understanding the details of aThe emphasis is on understanding the details of a

situation and deciding whether improvement issituation and deciding whether improvement is

desired or feasible.desired or feasible.

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Determining what changes be made.Determining what changes be made.

The intent of the systems investigation is to study aT

he intent of the systems investigation is to study abusiness process and evaluate it.business process and evaluate it.

Change should be a result, not an intent.Change should be a result, not an intent.

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Determining how best to solve an informationDetermining how best to solve an information

systems problem.systems problem.

Regardless of the organization, the analyst works onRegardless of the organization, the analyst works on

business problems.business problems.

It would be a mistake to distinguish betweenIt would be a mistake to distinguish between

business and systems problems, since there are nobusiness and systems problems, since there are nosystems problems that are not just businesssystems problems that are not just business

problems.problems.

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R esponsibility for ComputerR esponsibility for Computer

ProgrammingProgramming Do systems analysts write computer programs?Do systems analysts write computer programs?

Some do; they are frequently called programmerSome do; they are frequently called programmer

analysts.analysts. Do most analysts actually do computerDo most analysts actually do computer

programming?programming?

The answer varies from firm to firm.T

he answer varies from firm to firm.

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However, the bestHowever, the best--qualified and most valuablequalified and most valuable

systems analystssystems analysts know how to program know how to program ..

Systems analysts who have this skill are usually Systems analysts who have this skill are usually much more useful to organizations, since theirmuch more useful to organizations, since their

programming ability enables them to formulateprogramming ability enables them to formulate

better and more complete new applicationbetter and more complete new application

specifications.specifications.

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Changes in Systems Analysts·Changes in Systems Analysts·

R

esponsibilitiesR

esponsibilities At one time all systems analysts were specialistsAt one time all systems analysts were specialists

in computing, not business.in computing, not business.

Consequently, they had to be trained in businessConsequently, they had to be trained in businessfunctions before they could develop systems forfunctions before they could develop systems for

an organization.an organization.

The situation is changing as business peopleThe situation is changing as business people

learn more about computing.learn more about computing.

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Users (managers and employees) are becoming highly Users (managers and employees) are becoming highly

involved in systems development for several reasons:involved in systems development for several reasons:

Users have accumulated experience from working withUsers have accumulated experience from working with

applications that were developed for them earlier.applications that were developed for them earlier. Computers have become commonplace.Computers have become commonplace.

New entrants (users) in organizations have some backgroundNew entrants (users) in organizations have some background

knowledge of information systems.knowledge of information systems.

Development of endDevelopment of end--user computing.user computing. Availability of better systems development tools.Availability of better systems development tools.

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Who are the Users?Who are the Users?

EndEnd--usersusers

HandsHands--on userson users

Indirect usersIndirect users

User managersUser managers

Senior managersSenior managers

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Business Systems ConceptsBusiness Systems Concepts

In the broadest sense, aIn the broadest sense, a system system is simply a set of is simply a set of

components that interact to accomplish somecomponents that interact to accomplish some

purpose.purpose.

A business is also a system.A business is also a system.

Every business system depends on a more orEvery business system depends on a more or

less abstract entity called anless abstract entity called an information system information system ..

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This system is the means by which data flow This system is the means by which data flow

from one person or department to another andfrom one person or department to another and

can encompass everything from interoffice mailcan encompass everything from interoffice mail

and telephone links to a computer system thatand telephone links to a computer system that

generates periodic reports for various users.generates periodic reports for various users.

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Systems use a basic control model consisting of:Systems use a basic control model consisting of:

AA standard standard for acceptable performance.for acceptable performance.

A method of A method of measuring measuring actual performance.actual performance. A means forA means for c omparing c omparing actual performance against theactual performance against the

standard.standard.

A method forA method for feedba ck.feedba ck.

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Categories of Information SystemsCategories of Information Systems

Transaction Processing SystemsTransaction Processing Systems

Management Information SystemsManagement Information Systems

Decision Support SystemsDecision Support Systems Executive Information SystemsExecutive Information Systems

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System Dev elopment StrategiesSystem Dev elopment Strategies

Systems Development Life Cycle MethodSystems Development Life Cycle Method

Structured Analysis Development MethodStructured Analysis Development Method

Systems Prototype MethodSystems Prototype Method

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Classical Systems Dev elopment LifeClassical Systems Dev elopment Life

CycleCycle

Systems development, a process consisting of Systems development, a process consisting of

the two major types of systems analysis andthe two major types of systems analysis and

design, starts when management or sometimesdesign, starts when management or sometimes

systems development personnel realize that asystems development personnel realize that a

particular business system needs improvement.particular business system needs improvement.

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TheThe systems development life c y c le ( SDLC)systems development life c y c le ( SDLC) method ismethod isclassically thought of as the set of activities thatclassically thought of as the set of activities thatanalysts, designers, and users carry out toanalysts, designers, and users carry out to

develop and implement an information system.develop and implement an information system. In most business situations the activities are allIn most business situations the activities are all

closely related, usually inseparable, and even theclosely related, usually inseparable, and even the

order of the steps in these activities may beorder of the steps in these activities may bedifficult to determine.difficult to determine.

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The system development life cycle methodThe system development life cycle method

consists of the following activities:consists of the following activities:

Preliminary investigationPreliminary investigation

Determination of system requirementsDetermination of system requirements

Design of systemDesign of system

Development of softwareDevelopment of software

Systems testing Systems testing

Implementation and evaluationImplementation and evaluation

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Preliminary InvestigationPreliminary Investigation

Request clarificationRequest clarification

Feasibility study Feasibility study Technical feasibility Technical feasibility

Economic feasibility Economic feasibility

Operational feasibility Operational feasibility

Request approvalRequest approval

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Determination of System RequirementsDetermination of System Requirements

What is being done?What is being done?

How is it being done?How is it being done?

How frequently does it occur?How frequently does it occur?

How great is the volume of transactions or decisions?How great is the volume of transactions or decisions?

How well is the task being performed?How well is the task being performed?

Does a problem exist?Does a problem exist?

If a problem exists, how serious is it?If a problem exists, how serious is it?

If a problem exists, what is the underlying cause?If a problem exists, what is the underlying cause?

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Design of SystemDesign of System

The design of an information system produces theThe design of an information system produces the

details that state how a system will meet thedetails that state how a system will meet the

requirements identified during systems analysis.requirements identified during systems analysis.

Systems specialists often refer to this stage asSystems specialists often refer to this stage as logi c al logi c al

design design , in contrast to the process of developing , in contrast to the process of developing

program software, which is referred to asprogram software, which is referred to as physi c al physi c al design design ..

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Systems analysts begin the design process by identifying Systems analysts begin the design process by identifying

reports and other outputs the system will produce.reports and other outputs the system will produce.

Then the specific data on each are pinpointed.Then the specific data on each are pinpointed.

Usually, designers sketch the form or display as they expect itUsually, designers sketch the form or display as they expect itto appear when the system is complete.to appear when the system is complete.

This may be done on paper or on a computer display, using This may be done on paper or on a computer display, using

one of the automated system design tools available.one of the automated system design tools available.

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The systems design also describes the data to beThe systems design also describes the data to be

input, calculated, or stored.input, calculated, or stored.

Individual data items and calculation procedures areIndividual data items and calculation procedures are

written in detail.written in detail.

Designers select file structures and storage devices,Designers select file structures and storage devices,

such as magnetic disk, magnetic tape, or even papersuch as magnetic disk, magnetic tape, or even paper

files.files.

The procedures they write tell how to process theThe procedures they write tell how to process the

data and produce the output.data and produce the output.

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The documents containing the design specificationsThe documents containing the design specifications

portray the design in many different waysportray the design in many different ways ² ² charts,charts,

tables, and special symbols.tables, and special symbols.

The detailed design information is passed on to theThe detailed design information is passed on to theprogramming staff so that software development canprogramming staff so that software development can

begin.begin.

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Implementation and EvaluationImplementation and Evaluation

OperationalEvaluationOperationalEvaluation

OrganizationalI

mpactOrganizationalI

mpact User Manager AssessmentUser Manager Assessment

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Structured Analysis Dev elopmentStructured Analysis Dev elopment

MethodMethod

Many IS specialists acknowledge the difficulty of Many IS specialists acknowledge the difficulty of

fully understanding large, complex system.fully understanding large, complex system.

The structured analysis development method isT

he structured analysis development method isaimed at overcoming that difficulty throughaimed at overcoming that difficulty through

Partitioning the system into componentsPartitioning the system into components

Constructing a model of the systemConstructing a model of the system

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Structured AnalysisStructured Analysis

S tru c tured analysis S tru c tured analysis focuses on specifying what the systemfocuses on specifying what the systemor application is required to do.or application is required to do.

It does not state how the requirements should beIt does not state how the requirements should beaccomplished or how the application should beaccomplished or how the application should beimplemented.implemented.

Rather, it allows individuals to see logical elementsRather, it allows individuals to see logical elements(what the system should do) apart from the physical(what the system should do) apart from the physicalcomponents it uses (computers, terminals, storagecomponents it uses (computers, terminals, storage

systems, etc.).systems, etc.). Later a physical design can be developed that will beLater a physical design can be developed that will be

effective for the situation in which it is to be used.effective for the situation in which it is to be used.

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Elements of Structured AnalysisElements of Structured Analysis

Essential elements of structured analysis includeEssential elements of structured analysis includegraphic symbols, data flow diagrams, and agraphic symbols, data flow diagrams, and acentralized data dictionary.centralized data dictionary.

Graphic DescriptionGraphic Description ² ² one way to describe aone way to describe asystem is to prepare a narrative outlining itssystem is to prepare a narrative outlining itsfeatures, identifying the function it serves,features, identifying the function it serves,describing how it interacts with other elements,describing how it interacts with other elements,etc.etc.

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However, describing a large system in this mannerHowever, describing a large system in this mannerwould be most tedious and error pronewould be most tedious and error prone ² ² it is easy toit is easy toomit a detail to describe it in a manner that others may omit a detail to describe it in a manner that others may

not understand.not understand. Instead of words, structured analysis uses symbols, orInstead of words, structured analysis uses symbols, or

icons, to create a graphic model of the system.icons, to create a graphic model of the system.

Graphic model show details of the system withoutGraphic model show details of the system without

introducing manual or computer processes, tape or disk introducing manual or computer processes, tape or disk files, or program and operating procedures.files, or program and operating procedures.

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Data Flow DiagramsData Flow Diagrams ² ² The system model is termed aThe system model is termed a

data flow diagram ( DFD)data flow diagram ( DFD)..

A full description of a system actually consists of a setA full description of a system actually consists of a set

of data flow diagram.of data flow diagram.

Developing a description of the system using structuredDeveloping a description of the system using structured

analysis follows a topanalysis follows a top--down process.down process.

An initial overview model is ´explodedµ into moreAn initial overview model is ´explodedµ into moredetailed, lowerdetailed, lower--level diagrams that show additionallevel diagrams that show additional

features of the system.features of the system.

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Each process can be broken into a yet moreEach process can be broken into a yet more

detailed data flow diagram.detailed data flow diagram.

This may occur repeatedly until sufficient detailT

his may occur repeatedly until sufficient detailis described to allow the analyst to fully is described to allow the analyst to fully

understand the portion of the system underunderstand the portion of the system under

investigation.investigation.

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Data DictionaryData Dictionary ² ² All definitions of elementsAll definitions of elementsin the systemin the system ² ² data flows, processes, and datadata flows, processes, and datastoresstores ² ² are described in detail in a dataare described in detail in a data

dictionary.dictionary. If a project team member wants to know theIf a project team member wants to know the

definition of a data item name or the contents of definition of a data item name or the contents of a particular data flow, the information should bea particular data flow, the information should beavailable in the dictionary.available in the dictionary.

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Structured DesignStructured Design

S tru c tured design S tru c tured design , another element of structured analysis, another element of structured analysisthat utilizes graphic description, focuses on thethat utilizes graphic description, focuses on thedevelopment of software specifications.development of software specifications.

The goal of structured design is to create programsThe goal of structured design is to create programsconsisting of functionally independent modules thatconsisting of functionally independent modules thatperform relatively independently of one another.perform relatively independently of one another.

The approach not only leads to better programs, but,The approach not only leads to better programs, but,

because modules are independent of one another, willbecause modules are independent of one another, willfacilitate program maintenance when the need arises.facilitate program maintenance when the need arises.

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Structured design is a specific program designStructured design is a specific program design

technique, not a comprehensive design method.technique, not a comprehensive design method.

Thus, it does not specify file or database design, inputThus, it does not specify file or database design, input

or output layout, processing sequences, or the hardwareor output layout, processing sequences, or the hardwareon which the application will run.on which the application will run.

On the other hand, it does lead to the specification of On the other hand, it does lead to the specification of

program modules that are functionally independent.program modules that are functionally independent.

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The fundamental tool of structured design is theThe fundamental tool of structured design is the

structure chart.structure chart.

Like DFD, structure charts are graphic and avoidLike DFD, structure charts are graphic and avoid

specification of hardware or physical details.specification of hardware or physical details.

They are not intended to show program logic (a task They are not intended to show program logic (a task

for flowcharts).for flowcharts).

Instead, they describe the interaction betweenInstead, they describe the interaction betweenindependent modules and the data passing betweenindependent modules and the data passing between

modules that interact with one another.modules that interact with one another.

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Systems Prototype MethodSystems Prototype Method

The systems prototype method involves the userThe systems prototype method involves the user

more directly in the analysis and designmore directly in the analysis and design

experience than does the systems developmentexperience than does the systems development

life cycle (SDLC) or structured analysis method.life cycle (SDLC) or structured analysis method.

Prototyping is very effective under the correctPrototyping is very effective under the correct

circumstances.circumstances.

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What is Prototype?What is Prototype?

AA prototype prototype is a working systemis a working system ² ² not just an idea on papernot just an idea on paper ² ² that is developedthat is developedto test ideas and assumption about the new system.to test ideas and assumption about the new system.

Like any computerLike any computer--based system, it consists of working software that acceptsbased system, it consists of working software that acceptsinput, performs calculations, produces printed or displayed information, orinput, performs calculations, produces printed or displayed information, orperforms other meaningful activities.performs other meaningful activities.

It is the first version or iteration of an information systemIt is the first version or iteration of an information system ² ² an originalan originalmodel.model.

The design and the information produced by the system are evaluated by The design and the information produced by the system are evaluated by users.users.

This can be effectively done only if the data are real and the situations live.This can be effectively done only if the data are real and the situations live.

Changes are expected as the system is used.Changes are expected as the system is used.

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Systems analysts find prototypes to be mostSystems analysts find prototypes to be most

useful under the following conditions:useful under the following conditions:

No system with the characteristics of one proposedNo system with the characteristics of one proposed

has yet been constructed by the developers.has yet been constructed by the developers.

The essential features of the system are only partially The essential features of the system are only partially

known; others are not identifiable even throughknown; others are not identifiable even through

careful analysis of requirements.careful analysis of requirements.

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Experience in using the system will significantly addExperience in using the system will significantly add

to the list of requirements the system should meetto the list of requirements the system should meet

(more so than for any other development approach).(more so than for any other development approach).

Alternate versions of the system will evolve throughAlternate versions of the system will evolve throughexperience and additional development andexperience and additional development and

refinement of its features.refinement of its features.

The system user(s) will participate in theThe system user(s) will participate in the

development process.development process.

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These are the steps in the prototyping process:These are the steps in the prototyping process:

Identify the user·s known information requirements andIdentify the user·s known information requirements and

features needed in the system.features needed in the system.

Develop a working prototype.Develop a working prototype. Use the prototype, noting needed enhancements andUse the prototype, noting needed enhancements and

changes. These expand the list of known systemchanges. These expand the list of known system

requirements.requirements.

Revise the prototype based on information gained throughRevise the prototype based on information gained throughuser experience.user experience.

Repeat these steps as needed to achieve a satisfactory system.Repeat these steps as needed to achieve a satisfactory system.

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Tools for System Dev elopmentTools for System Dev elopment

Analysis ToolsAnalysis Tools ² ² assist systems specialists inassist systems specialists in

documenting an existing system whether manualdocumenting an existing system whether manual

or automated, and determining the requirementsor automated, and determining the requirements

for a new application. These tools include:for a new application. These tools include:

Data Collection ToolsData Collection Tools ² ² Capture details describing Capture details describing

current systems and procedures. Documentcurrent systems and procedures. Document

processes and decision activities. Used to assist inprocesses and decision activities. Used to assist inrequirements identification.requirements identification.

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Charting ToolsCharting Tools ² ² Create graphic representations of Create graphic representations of systems and activities. Assist in the drawing andsystems and activities. Assist in the drawing andrevision of data flow diagrams and icons associatedrevision of data flow diagrams and icons associatedwith structured analysis. Also include flowcharting with structured analysis. Also include flowcharting programs.programs.

Dictionary ToolsDictionary Tools ² ² Record and maintainRecord and maintaindescriptions of system elements, such as data items,descriptions of system elements, such as data items,processes, and data stores. Often provide theprocesses, and data stores. Often provide thecapability to examine system descriptions forcapability to examine system descriptions forinconsistent or incomplete descriptions. May alsoinconsistent or incomplete descriptions. May alsoinclude the capability to report where items are used.include the capability to report where items are used.

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Design ToolsDesign Tools ² ² assist in formulating the features of aassist in formulating the features of a

system that will meet the requirements outlined during system that will meet the requirements outlined during

the analysis activities:the analysis activities:

Specification ToolsSpecification Tools ² ² assist in stating the features thatassist in stating the features thatshould be included in application, such as input, output,should be included in application, such as input, output,

processing, and control specifications. May also include toolsprocessing, and control specifications. May also include tools

for creating data specifications.for creating data specifications.

LayoutT

oolsLayoutT

ools ² ² used to describe the position of data,used to describe the position of data,messages, and headings on display screens, reports, and othermessages, and headings on display screens, reports, and other

input and output media.input and output media.

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Dev elopment ToolsDev elopment Tools ² ² aid the analyst in translating aid the analyst in translating

designs into functioning applications:designs into functioning applications:

Software Engineering ToolsSoftware Engineering Tools ² ² assist in formulating assist in formulating

software design, including procedures and controls, as well assoftware design, including procedures and controls, as well asdocumentation for the design.documentation for the design.

Code GeneratorsCode Generators ² ² produce source code and working produce source code and working

applications from functional specifications that are wellapplications from functional specifications that are well

articulated.articulated.

Testing ToolsTesting Tools ² ² aid in evaluating a system or portion of aaid in evaluating a system or portion of a

system specifications.system specifications.

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Documents

Introduction to Systems Analysis & Design