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

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

attheuniversitylevelwhenusedinconjunctionwithSoftwareEngineering:APractitioner'sApproach,7/e.Anyotherreproductionoruse

isprohibitedwithouttheexpresswrittenpermissionoftheauthor.AllcopyrightinformationMUSTappeariftheseslidesarepostedonawebsitefors

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

rolling,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◼Analyzerisks◼Riskanalysisisconsideredindet

ailinChapter25.◼Definerequiredresources◼Determinerequirehumanresources◼Definereusablesoftwareresources◼Identifyenvironmentalresources第3页，共28页。4www.n

iuwk.com牛牛文库文档分享ProjectPlanningTaskSet-II◼Estimatecostandeffort◼Decomposetheproblem◼Developtwoormoreestimatesusingsize,functionpoints,pr

ocesstasksoruse-cases◼Reconciletheestimates◼Developaprojectschedule◼SchedulingisconsideredindetailinChapter2

7.•Establishameaningfultaskset•Defineatasknetwork•Useschedulingtoolstodevelopatimelinechart•Defineschedu

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

reengineeringeffortrequires◼experience◼accesstogoodhistoricalinformation(metrics)◼thecouragetocommittoquantitativepredictionswhenqualitativ

einformationisallthatexists◼Estimationcarriesinherentriskandthisriskleadstouncertainty第5页，共28页。6www.niuwk.com牛牛文库文档分享WriteitDown!SoftwareProjec

tPlanProjectScopeEstimatesRisksScheduleControlstrategy第6页，共28页。7www.niuwk.com牛牛文库文档分享ToUnderstandScope...◼Understandthecustomersneeds◼understandtheb

usinesscontext◼understandtheprojectboundaries◼understandthecustomer’smotivation◼understandthelikelypathsforchange◼understandthat...Evenwh

enyouunderstand,nothingisguaranteed!第7页，共28页。8www.niuwk.com牛牛文库文档分享WhatisScope?◼Softwarescopedescribes◼thefunc

tionsandfeaturesthataretobedeliveredtoend-users◼thedatathatareinputandoutput◼the“content”thatispresen

tedtousersasaconsequenceofusingthesoftware◼theperformance,constraints,interfaces,andreliabilitythatboundthesyst

em.◼Scopeisdefinedusingoneoftwotechniques:•Anarrativedescriptionofsoftwarescopeisdevelopedaftercommunicationwithallstakeholders.•Asetofuse-casesisde

velopedbyend-users.第8页，共28页。9www.niuwk.com牛牛文库文档分享ResourcesprojectpeopleskillsnumberlocationreusablesoftwareOTScomponentsfull-experiencecomponent

snewcomponentspart.-experiencecomponentsenvironmenthardwaresoftwaretoolsnetworkresources第9页，共28页。10www.niuwk.com牛牛文库文档分享ProjectEstimati

on◼Projectscopemustbeunderstood◼Elaboration(decomposition)isnecessary◼Historicalmetricsareveryhelpful◼Atleasttwodiffe

renttechniquesshouldbeused◼Uncertaintyisinherentintheprocess第10页，共28页。11www.niuwk.com牛牛文库文档分享EstimationTechniques◼Past(similar)projectexperie

nce◼Conventionalestimationtechniques◼taskbreakdownandeffortestimates◼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◼Predicatedon…◼thedegreetowhichtheplannerhasproperlyestimatedthesizeoftheprodu

cttobebuilt◼theabilitytotranslatethesizeestimateintohumaneffort,calendartime,anddollars(afunctionoftheavailabil

ityofreliablesoftwaremetricsfrompastprojects)◼thedegreetowhichtheprojectplanreflectstheabilitiesoftheso

ftwareteam◼thestabilityofproductrequirementsandtheenvironmentthatsupportsthesoftwareengineeringeffort.第12页，共28页。13www.niuwk.com牛牛文

库文档分享FunctionalDecompositionfunctionaldecompositionStatementofScopePerformaGrammatical“parse”第13页，共28页。14www.niuwk.com牛牛

文库文档分享ConventionalMethods:LOC/FPApproach◼computeLOC/FPusingestimatesofinformationdomainvalues◼usehistoricaldat

atobuildestimatesfortheproject第14页，共28页。15www.niuwk.com牛牛文库文档分享Example:LOCApproachAverageproductivityforsyste

msofthistype=620LOC/pm.Burdenedlaborrate=$8000permonth,thecostperlineofcodeisapproximately$13.BasedontheLOCestimateandthehistoricalp

roductivitydata,thetotalestimatedprojectcostis$431,000andtheestimatedeffortis54person-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=375organization

alaverageproductivity=6.5FP/pm.burdenedlaborrate=$8000permonth,approximately$1230/FP.BasedontheFPestimateandthehistoricalproductivitydata,to

talestimatedprojectcostis$461,000andestimatedeffortis58person-months.第16页，共28页。17www.niuwk.com牛牛文库文档分享Process-

BasedEstimationObtainedfrom“processframework”applicationfunctionsframeworkactivitiesEffortrequiredtoaccomplisheachframeworkactivityforeachapplication

function第17页，共28页。18www.niuwk.com牛牛文库文档分享Process-BasedEstimationExampleActivityTaskFunctionUICF2DGA3DGADSMPCFCGDFDAMTo

tals%effortCCPlanningRiskAnalysisEngineeringConstructionReleaseTotalsCEanalysisdesigncodetest0.250.250.253.5020.504.5016.504

6.001%1%1%8%45%10%36%CC=customercommunicationCE=customerevaluation0.500.750.500.500.500.252.504.004.003.003.002.000.400

.601.001.000.750.505.002.003.001.501.501.508.407.358.506.005.754.250.502.000.502.005.00n/an/an/an/an/an/an/aBasedonanaverageburdenedlabor

rateof$8,000permonth,thetotalestimatedprojectcostis$368,000andtheestimatedeffortis46person-months.第18页，共28页。19www.niuwk.com牛牛文库文档分享Tool-BasedEst

imationprojectcharacteristicscalibrationfactorsLOC/FPdata第19页，共28页。20www.niuwk.com牛牛文库文档分享EstimationwithUse-Casesusecasesscenariospag

esÊscenariospagesLOCLOCestimateesubsystem6106Ê1255603,366subsystemgroup10208Ê168310031,233esubsystemgroup565Ê10616507,970ÊÊÊÊstimateÊ

ÊÊÊ42,568UserinterfacesubsystemEngineeringsubsystemgroupInfrastructuresubsystemgroupTotalLOCestimateUsing620LOC/pmastheaverageproductivi

tyforsystemsofthistypeandaburdenedlaborrateof$8000permonth,thecostperlineofcodeisapproximately$13.Basedontheuse-caseestimat

eandthehistoricalproductivitydata,thetotalestimatedprojectcostis$552,000andtheestimatedeffortis68person-months.第20页，共28页。21www.ni

uwk.com牛牛文库文档分享EmpiricalEstimationModelsGeneralform:effort=tuningcoefficient*sizeexponentusuallyderivedasperson-monthsofeffortrequiredeitherac

onstantoranumberderivedbasedoncomplexityofprojectusuallyLOCbutmayalsobefunctionpointempiricallyderive

d第21页，共28页。22www.niuwk.com牛牛文库文档分享COCOMO-II◼COCOMOIIisactuallyahierarchyofestimationmodelsthataddressthefollowingareas:•Applicationcompositio

nmodel.Usedduringtheearlystagesofsoftwareengineering,whenprototypingofuserinterfaces,considerationofsoftwareandsysteminteraction,assessment

ofperformance,andevaluationoftechnologymaturityareparamount.•Earlydesignstagemodel.Usedoncerequirementshavebeenstabilizedandbasicsoftwarearchitectu

rehasbeenestablished.•Post-architecture-stagemodel.Usedduringtheconstructionofthesoftware.第22页，共28页。23ww

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

monthsorperson-yearst=projectdurationinmonthsoryearsB=“specialskillsfactor”P=“productivityparameter”第23页，共28页。24w

ww.niuwk.com牛牛文库文档分享EstimationforOOProjects-I◼Developestimatesusingeffortdecomposition,FPanalysis,andanyothermethodthatisapplicableforconventionalapp

lications.◼Usingobject-orientedrequirementsmodeling(Chapter6),developuse-casesanddetermineacount.◼Fromtheanalysismodel,determinethenumberofkeyclasse

s(calledanalysisclassesinChapter6).◼Categorizethetypeofinterfacefortheapplicationanddevelopamultiplierforsupportclasses:◼InterfacetypeMu

ltiplier◼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◼Multiplythenum

berofkeyclasses(step3)bythemultipliertoobtainanestimateforthenumberofsupportclasses.◼Multiplythetotalnumberofcl

asses(key+support)bytheaveragenumberofwork-unitsperclass.LorenzandKiddsuggest15to20person-daysperclass.◼Cross

checktheclass-basedestimatebymultiplyingtheaveragenumberofwork-unitsperuse-case第25页，共28页。26www.niuwk.com牛牛文库文档分享EstimationforAgilePr

ojects◼Eachuserscenario(amini-use-case)isconsideredseparatelyforestimationpurposes.◼Thescenarioisdecomposedintothesetofsoftwareengineering

tasksthatwillberequiredtodevelopit.◼Eachtaskisestimatedseparately.Note:estimationcanbebasedonhistoricaldata,anemp

iricalmodel,or“experience.”◼Alternatively,the‘volume’ofthescenariocanbeestimatedinLOC,FPorsomeothervolume-orientedmeasure(e.g.,use-casecount).◼Es

timatesforeachtaskaresummedtocreateanestimateforthescenario.◼Alternatively,thevolumeestimateforthescenarioistranslatedintoeffortusinghistorical

data.◼Theeffortestimatesforallscenariosthataretobeimplementedforagivensoftwareincrementaresummedtodeveloptheeffortestimate

fortheincrement.第26页，共28页。27www.niuwk.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(pathpr

obability)x(estimatedpathcost)iiForexample,theexpectedcosttobuildis:expectedcost=0.30($380K)+0.70($450K)similarly,expectedcost=$382Kexpectedcos

t=$267Kexpectedcost=$410Kbuildreusebuycontrexpectedcost==$429K第28页，共28页。