高级需求工程 Advanced Requirement Engineering -- Ch.pdf

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1、CHAPTER5ValidatingRequirementsIntroductionChapter4discussedanumberofmodellingformalismswhichcanbeusedforcreatingafunctionalrequirementsmodel.Theuseofasingleformalismoracombinationofthem,forexampleentities/relationships,rules,statetransitiondiagramsetc.,willresultinamodelo

2、fwhattheanalystperceivestobetheuserrequirementsforasoftwaresystem.Withcarefulchecking,possiblywithsomehelpfromanautomatedCASEtool(suchasthosediscussedinChapter6),theanalystcanbecomefairlyconvincedthattherequirementsmodelisacorrectone,wherethetermcorrectmeansthatthemodelwi

3、llnotcontainillogicalorself-contradictingdefinitions.Thereisaproblemwiththeaboveapproachhowever.Acorrectrequirementsmodelisnotnecessarilytherightrequirementsmodel.Whathasbeenthoughttobetheuser'sproblemcansometimesbesomethingtotallyirrelevant,i.e.asituationcanoccurwheretim

4、eandeffortisspentanalysingthewrongproblem.SuchasituationisillustratedinFigure5.1.Figure5.1:Solvingthewrongproblem.Chapter3identifiedthemaincausesforsuchmisconceptionstobe:•difficultyinelicitingtherequirementsfromauser.(InExpertSystemterminologythisiscalledtheknowledgeacqu

5、isitionbottleneck)•difficultyinestablishingacommonframeworkofunderstandingbetweentheanalystandtheuser,i.e.makingthemspeakthesamelanguage.Obviously,wastingprecioustimeandresourcesinsolvingthewrongproblemsissomethingill-afforded.Itisthereforeimportanttomakesureatafairlyearl

6、ystagethattheanalysedproblemisindeedtheuser'sproblemandthattheresultingrequirementsmodelwillbeafaithfulrepresentationoftheuser'sdemandforacomputersolutiontohis/herproblem.Requirementsvalidationistheprocessofcertifyingtherequirementsmodelforcorrectnessagainsttheuser'sinten

7、tionAssuchrequirementsvalidationhelpstodotherightthingincontrastwiththecarefulfollowingofamodellingapproachwhichhelpsindoingthethingright.Section5.1providesmoreargumentsinfavourofanearlyvalidationofrequirementswhichwillavoidcorrectingexpensivemistakeslateroninthesoftwarel

8、ifecycle.Section2_______________________________________________________________________________