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System Life Cycle

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Major Stages

AnalysisDesignOperationInstallation

Maintenance

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Analysis

Collection and examination of dataUsers requirements Flow of data through existing system

Feasibility Report

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Analysis

DATA COLLECTIONNeeded for a clear picture of problem;carried out in a systematic and thoroughway.

It identifies:Who inputs data in the systemWhat form of data is in

Any validation neededWhat processing is done to produceoutputs

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Analysis

DATA COLLECTION TECHNIQUESFact Finding Interviews

QuestionnairesSearch existing documentsSearch literature of other solutions to

the same problemObserve people working with existingsystem

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Method Advantages Disadvantages

Inteview More detailed data;interesting topicspursued.

Time consuming; lackof classify or quantifydata

Questionnaire More people; easy toanalyse

People may notanswer; questions can

be confusingExisting Docs Input / Output data

indentifiedDocuments mayinclude part of the story

LiteratureSearch

Save work if problemalready solved

Fine detail of solutionnot provided

Observation Able to find out otherthings

Time consuming;observer can affect

process

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AnalysisREQUIREMENTS SPECIFICATION

What the system is expected to do and how;Includes: costs of builiding, testing and running thesystem (Hardware & Software) and time forcompletion.

It includes:List of hardware and software toolsDescription of functions of H / S in the completedsystem

Formal agreement on performance of systemList of personnel and tasks allocated to each oneGANTT and PERT CHARTS can be used to trackprogress

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Gantt Chart

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Pert Chart

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AnalysisFEASIBILITY REPORT

After the requirements have been identified a reportcan be produced that wouldEstimate costsIdentifies benefits

Estimates how long the project will takeOutlines potential difficultiesOn the basis of this report a decision will be taken

Detailed Requirements Specifications (alsocalled feasibility report) Should include analysis of any riskReview other solutions produced in the past

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AnalysisALTERNATIVE SOLUTIONS

General Application Software : leastexpensive but may not have all featuresneeded

Specific applications packages : moreexpensive; provides features typically usedTailor made software : written from scratch,

more expensive and more time-consuming. Itwill do exactly what the customer needs.

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AnalysisIMPORTANCE OF FORMULATING A

PROBLEM PRECISELY

If a team is working on the problem, ALLneed to be communicatedUsers need to understand exactly was will bedone (changes implied)Costs can be calculated and weighed againstbenefits (written in Feasibility Report)System can be properly tested

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System Design

Software and hardware aspects clearly

definedFile design and suitable data structures andalgorithmsUML (Unified Modelling Language) to define

data flow between objects and methodsMore detailed feasibility report with costbenefit analysis

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Flowchart:

used todescribealgorithms,althoughpseudocode ispreferred.

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Data flowdiagrams: refer to dataobjects andprocesses(people,papers,

computer files,etc).

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Module

Diagram: used to split alarge problem

into smallerones (stepwiserefinement).Easier to solveand dividebetween team.

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Operation

Plan of development of a solutionWith complex systems, important to

identify the discrete tasks to becompletedGANTT chart: graphical representationof the duration of tasks against theprogression of time PERT charts

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SYSTEM TESTING

Functional testing : what is expected tohappen when buttons are pressed

Testing with Input dataNormal Data : also data at the limit should bechecked

Extreme Data : outside the normal limits Abnormal Data : unexpected data

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Installation or ImplementationSeveral ways of undertaking the processDifferent methods of changeover

Parallel runningPhased introductionBig Bang or direct changeover

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MaintenanceExpensive & time consuming (easier and

cheaper if modular design)Periodic reviews of the system

Fact finding (interview, questionnaires, etc)

Analysis

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System Life Cycle