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1、SoftwareEngineeringEvolution&NanagementEffortEstimationCOCOMO-AnEmpiricalEstimationModelforEffortIntroduction:Thestructureofempiricalestimationmodelsisaformula,derivedfromdatacollectedfrompastsoftwareprojects,thatusessoftwaresizetoestimateeffort.Size,itself,isanestimate,described
2、aseitherlinesofcode(LOC)orfunctionpoints(FP).Noestimationmodelisappropriateforalldevelopmentenvironments,developmentprocesses,orapplicationtypes.Modelsmustbecustomised(valuesintheformulamustbealtered)sothatresultsfromthemodelagreewiththedatafromtheparticularenvironment.Thetypical
3、formulaofestimationmodelsis:E=a+b(S)cwhere;Erepresentseffort,inpersonmonths,Sisthesizeofthesoftwaredevelopment,inLOCorFP,and,a,b,andcarevaluesderivedfromdata.Therelationshipseenbetweendevelopmenteffortandsoftwaresizeisgenerally:ESThisgraphdemonstratesthattheamountofeffortaccelera
4、tesassizeincreases,i.e.,thevaluecinthetypicalformulaaboveisgreaterthan1.COCOMO:WhenBarryBoehmwrote'SoftwareEngineeringEconomics',publishedin1981,heintroducedanempiricaleffortestimationmodel(COCOMO-COnstructiveCOstMOdel)thatisstillreferencedbythesoftwareengineeringcommunity.Themod
5、elhasbeenreviewedsince1981anddetailsoftherevisedandupdatedCOCOMO2model,canbeobtainedat:http://sunset.usc.edu/research/index.html.TheoriginalCOCOMOmodelwasasetofmodels;3developmentmodes(organic,semi-detached,andembedded)and3levels(basic,intermediate,andadvanced).COCOMOmodellevels:
6、Basic-predictedsoftwaresize(linesofcode)wasusedtoestimatedevelopmenteffort.Intermediate-predictedsoftwaresize(linesofcode),plusasetof15subjectivelyassessed'costdrivers'wasusedtoestimatedevelopmenteffort.page:4of4SoftwareEngineeringEvolution&NanagementEffortEstimationAdvanced-onto
7、poftheintermediatemodel,theadvancedmodelallowsphase-basedcostdriveradjustmentsandsomeadjustmentsatthemodule,component,andsystemlevel.COCOMOdevelopmentmodes:Organic-smallrelativelysmall,simplesoftwareprojectsinwhichsmallteamswithgoodapplicationexperienceworktoasetofflexiblerequire
8、ments.Embedded-thesoftwareprojecthastigh