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1www.niuwk.com牛牛文库文档分享Chapter20◼EstimationforSoftwareProjectsSlideSettoaccompanySoftwareEngineering:APractitioner’sApproach,7/ebyRogerS.Pre

ssmanSlidescopyright©1996,2001,2005,2009byRogerS.PressmanFornon-profiteducationaluseonlyMaybereproducedONLYforstudentuse

attheuniversitylevelwhenusedinconjunctionwithSoftwareEngineering:APractitioner'sApproach,7/e.Anyotherrep

roductionoruseisprohibitedwithouttheexpresswrittenpermissionoftheauthor.AllcopyrightinformationMUSTapp

eariftheseslidesarepostedonawebsiteforstudentuse.第1页，共28页。2www.niuwk.com牛牛文库文档分享SoftwareProjectPlanningTheoverallgoalofprojectplanningistoestabli

shapragmaticstrategyforcontrolling,tracking,andmonitoringacomplextechnicalproject.Why?Sotheendresultgetsdoneontime,withquality!第

2页，共28页。3www.niuwk.com牛牛文库文档分享ProjectPlanningTaskSet-I◼Establishprojectscope◼Determinefeasibility◼Analyzerisk

s◼RiskanalysisisconsideredindetailinChapter25.◼Definerequiredresources◼Determinerequirehumanresources◼Definereusablesoftwareresources◼Id

entifyenvironmentalresources第3页，共28页。4www.niuwk.com牛牛文库文档分享ProjectPlanningTaskSet-II◼Estimatecostandeff

ort◼Decomposetheproblem◼Developtwoormoreestimatesusingsize,functionpoints,processtasksoruse-cases◼Reconciletheestimates◼Developaprojectsch

edule◼SchedulingisconsideredindetailinChapter27.•Establishameaningfultaskset•Defineatasknetwork•Useschedulingtoolstodevelopatimelinechart•Defin

escheduletrackingmechanisms第4页，共28页。5www.niuwk.com牛牛文库文档分享Estimation◼Estimationofresources,cost,andscheduleforasoftwareengineerin

geffortrequires◼experience◼accesstogoodhistoricalinformation(metrics)◼thecouragetocommittoquantitativepredictionswhenquali

tativeinformationisallthatexists◼Estimationcarriesinherentriskandthisriskleadstouncertainty第5页，共28页。6www.niuwk.com牛牛文库文档分享WriteitD

own!SoftwareProjectPlanProjectScopeEstimatesRisksScheduleControlstrategy第6页，共28页。7www.niuwk.com牛牛文库文档分享ToUnderstandScope...◼Unders

tandthecustomersneeds◼understandthebusinesscontext◼understandtheprojectboundaries◼understandthecustomer’smotiv

ation◼understandthelikelypathsforchange◼understandthat...Evenwhenyouunderstand,nothingisguaranteed!第7页，共28页。8www.niuwk.com牛牛文库文档分

享WhatisScope?◼Softwarescopedescribes◼thefunctionsandfeaturesthataretobedeliveredtoend-users◼thedatathatare

inputandoutput◼the“content”thatispresentedtousersasaconsequenceofusingthesoftware◼theperformance,constraints,interfaces,and

reliabilitythatboundthesystem.◼Scopeisdefinedusingoneoftwotechniques:•Anarrativedescriptionofsoftwarescopeisdevelopedaftercommunicationwithallst

akeholders.•Asetofuse-casesisdevelopedbyend-users.第8页，共28页。9www.niuwk.com牛牛文库文档分享ResourcesprojectpeopleskillsnumberlocationreusablesoftwareO

TScomponentsfull-experiencecomponentsnewcomponentspart.-experiencecomponentsenvironmenthardwaresoftwaretoolsnetworkresources第9页，共

28页。10www.niuwk.com牛牛文库文档分享ProjectEstimation◼Projectscopemustbeunderstood◼Elaboration(decomposition)isnecessary◼Historicalmetricsare

veryhelpful◼Atleasttwodifferenttechniquesshouldbeused◼Uncertaintyisinherentintheprocess第10页，共28页。11www.niuwk.com牛牛文库文

档分享EstimationTechniques◼Past(similar)projectexperience◼Conventionalestimationtechniques◼taskbreakdownandeffortesti

mates◼size(e.g.,FP)estimates◼Empiricalmodels◼Automatedtools第11页，共28页。12www.niuwk.com牛牛文库文档分享EstimationAccuracy◼Predi

catedon…◼thedegreetowhichtheplannerhasproperlyestimatedthesizeoftheproducttobebuilt◼theabilitytotranslatethesizeestimat

eintohumaneffort,calendartime,anddollars(afunctionoftheavailabilityofreliablesoftwaremetricsfrompastprojects)◼thedegreeto

whichtheprojectplanreflectstheabilitiesofthesoftwareteam◼thestabilityofproductrequirementsandtheenvironmentthatsupp

ortsthesoftwareengineeringeffort.第12页，共28页。13www.niuwk.com牛牛文库文档分享FunctionalDecompositionfunctionalde

compositionStatementofScopePerformaGrammatical“parse”第13页，共28页。14www.niuwk.com牛牛文库文档分享ConventionalMethods:LO

C/FPApproach◼computeLOC/FPusingestimatesofinformationdomainvalues◼usehistoricaldatatobuildestimatesfortheproject第14页，共28页。15www.niuwk.

com牛牛文库文档分享Example:LOCApproachAverageproductivityforsystemsofthistype=620LOC/pm.Burdenedlaborrate=$8000permonth,thecostperlineofcodeisa

pproximately$13.BasedontheLOCestimateandthehistoricalproductivitydata,thetotalestimatedprojectcostis$431,000andtheestimate

deffortis54person-months.第15页，共28页。16www.niuwk.com牛牛文库文档分享Example:FPApproachTheestimatednumberofFPisderived:

FPestimated=count-total3[0.65+0.013S(Fi)]FPestimated=375organizationalaverageproductivity=6.5FP/pm.burdenedlaborrate=$8000permonth,app

roximately$1230/FP.BasedontheFPestimateandthehistoricalproductivitydata,totalestimatedprojectcostis$461,000an

destimatedeffortis58person-months.第16页，共28页。17www.niuwk.com牛牛文库文档分享Process-BasedEstimationObtainedfrom“pr

ocessframework”applicationfunctionsframeworkactivitiesEffortrequiredtoaccomplisheachframeworkactivityforeachapplicationfunction第17页，共2

8页。18www.niuwk.com牛牛文库文档分享Process-BasedEstimationExampleActivityTaskFunctionUICF2DGA3DGADSMPCFCGDFDAMTotals%effortCCPla

nningRiskAnalysisEngineeringConstructionReleaseTotalsCEanalysisdesigncodetest0.250.250.253.5020.504.5016.5046.001%1%1%8%4

5%10%36%CC=customercommunicationCE=customerevaluation0.500.750.500.500.500.252.504.004.003.003.002.000.400.601.001.000.750.505.00

2.003.001.501.501.508.407.358.506.005.754.250.502.000.502.005.00n/an/an/an/an/an/an/aBasedonanaverageburdened

laborrateof$8,000permonth,thetotalestimatedprojectcostis$368,000andtheestimatedeffortis46person-months.第

18页，共28页。19www.niuwk.com牛牛文库文档分享Tool-BasedEstimationprojectcharacteristicscalibrationfactorsLOC/FPdata第19页，共28页。20www.niuwk.com牛牛文库文档分享E

stimationwithUse-CasesusecasesscenariospagesÊscenariospagesLOCLOCestimateesubsystem6106Ê1255603,366subsystemgroup10208Ê1

68310031,233esubsystemgroup565Ê10616507,970ÊÊÊÊstimateÊÊÊÊ42,568UserinterfacesubsystemEngineeringsubsystemgroupInfrastructuresubsystemgroupTo

talLOCestimateUsing620LOC/pmastheaverageproductivityforsystemsofthistypeandaburdenedlaborrateof$8000permonth,thecostperlineofcodeisap

proximately$13.Basedontheuse-caseestimateandthehistoricalproductivitydata,thetotalestimatedprojectcostis$5

52,000andtheestimatedeffortis68person-months.第20页，共28页。21www.niuwk.com牛牛文库文档分享EmpiricalEstimationModelsGeneralfo

rm:effort=tuningcoefficient*sizeexponentusuallyderivedasperson-monthsofeffortrequiredeitheraconstantoranumberderi

vedbasedoncomplexityofprojectusuallyLOCbutmayalsobefunctionpointempiricallyderived第21页，共28页。22www.niuwk.com牛

牛文库文档分享COCOMO-II◼COCOMOIIisactuallyahierarchyofestimationmodelsthataddressthefollowingareas:•Applicationcompositionmodel.Usedduringtheearlystagesofs

oftwareengineering,whenprototypingofuserinterfaces,considerationofsoftwareandsysteminteraction,assessmentofperformance,andev

aluationoftechnologymaturityareparamount.•Earlydesignstagemodel.Usedoncerequirementshavebeenstabilizedandb

asicsoftwarearchitecturehasbeenestablished.•Post-architecture-stagemodel.Usedduringtheconstructionofthesoftware.第22页，共28页。23www.niuwk.com

牛牛文库文档分享TheSoftwareEquationAdynamicmultivariablemodelE=[LOCxB0.333/P]3x(1/t4)whereE=effortinperson-monthsorperson-ye

arst=projectdurationinmonthsoryearsB=“specialskillsfactor”P=“productivityparameter”第23页，共28页。24www.niuwk.com牛牛文库文档分享EstimationforOOProjects-

I◼Developestimatesusingeffortdecomposition,FPanalysis,andanyothermethodthatisapplicableforconventionalapplic

ations.◼Usingobject-orientedrequirementsmodeling(Chapter6),developuse-casesanddetermineacount.◼Fromtheanalysismodel,de

terminethenumberofkeyclasses(calledanalysisclassesinChapter6).◼Categorizethetypeofinterfacefortheapplicationanddevelopamultiplierforsupportcl

asses:◼InterfacetypeMultiplier◼NoGUI2.0◼Text-baseduserinterface2.25◼GUI2.5◼ComplexGUI3.0第24页，共28页。25www.niuwk.

com牛牛文库文档分享EstimationforOOProjects-II◼Multiplythenumberofkeyclasses(step3)bythemultipliertoobtainanestimatefor

thenumberofsupportclasses.◼Multiplythetotalnumberofclasses(key+support)bytheaveragenumberofwork-unitsperclass.LorenzandKidd

suggest15to20person-daysperclass.◼Crosschecktheclass-basedestimatebymultiplyingtheaveragenumberofwork-unitsperuse-case第25页，共28页。26www.niuwk.com牛牛文

库文档分享EstimationforAgileProjects◼Eachuserscenario(amini-use-case)isconsideredseparatelyforestimationpurposes

.◼Thescenarioisdecomposedintothesetofsoftwareengineeringtasksthatwillberequiredtodevelopit.◼Eachtaskisestimat

edseparately.Note:estimationcanbebasedonhistoricaldata,anempiricalmodel,or“experience.”◼Alternatively,the‘volume’ofthescenariocanbeestima

tedinLOC,FPorsomeothervolume-orientedmeasure(e.g.,use-casecount).◼Estimatesforeachtaskaresummedtocreateanes

timateforthescenario.◼Alternatively,thevolumeestimateforthescenarioistranslatedintoeffortusinghistoricaldata.◼Theeffortestimatesforallscenarios

thataretobeimplementedforagivensoftwareincrementaresummedtodeveloptheeffortestimatefortheincrement.第26页，共28页。27www.niu

wk.com牛牛文库文档分享TheMake-BuyDecision第27页，共28页。28www.niuwk.com牛牛文库文档分享ComputingExpectedCost(pathprobability)x(estimatedpathcost)iiForexample,theexp

ectedcosttobuildis:expectedcost=0.30($380K)+0.70($450K)similarly,expectedcost=$382Kexpectedcost=$267Kexpectedco

st=$410Kbuildreusebuycontrexpectedcost==$429K第28页，共28页。