軟件工程專業(yè)英語-Software Reengineering

我們畢業(yè)啦其實是答辯的標(biāo)題地方軟件工程專業(yè)英語SOFTWAREENGINEERINGESSENTIALS22.1SOFTWAREENGINEERING2.2SOFTWAREREENGINEERING2.3

REVERSEENGINEERINGSUMMARYCHAPTER2

SOFTWAREREENGINEERING2.1SOFTWAREENGINEERING3Inthelongperiodofpracticeinbuildingsoftware,softwaredevelopershavedrawnaconclusion:softwareinallofitsformsandacrossallofitsapplicationdomainsshouldbeengineered.4SoftwareEngineeringOverviewSoftwareProcessModelPhasesofSoftwareDevelopmentMethodologyofSoftwareDevelopment1.Whatissoftwareengineering?Softwareengineeringistheestablishmentanduseofsoundengineeringprinciplesinordertoobtaineconomicallysoftwarethatisreliableandworksefficientlyonrealmachines.SoftwareEngineering:(1)Theapplicationofasystematic,disciplined,andquantifiableapproachtothedevelopment,operation,andmaintenanceofsoftware;thatis,theapplicationofengineeringtosoftware.(2)Thestudyofapproachesasin(1).------TheIEEEhasdevelopedamorecomprehensivedefinition2.OriginofsoftwareengineeringInordertoreducetheinfluencesofsoftwarecrises,thecomputerscientistsdiscussedthesoftwarecrisesproblemsatinternationalconferenceinGermanin1968,andthenameof“SoftwareEngineering”wasfirstputforwardandadopted.Fromthenon,SoftwareEngineering,asanewengineeringdiscipline,wasborn.3.Whatisalifecycleofsoftware?Theperiodoftimethatisneededtocreatenewsoftware,iscalledthelifecycleofsoftware,whichstartsfromthetimeofproblemdefinition,thendevelopment,deploymentandmaintenance,tillthemomentofretirement.

4.SoftwareprocessAsoftwareprocessisacollectionofactivities,actions,andtasksperformedwhensoftwareisbeingbuilt.Anactivitystrivestoachieveabroadobjective(e.g.,communicationwithusers)andisappliedregardlessoftheapplicationdomain,sizeoftheproject,complexityoftheeffort,ordegreeofrigorwithwhichsoftwareengineeringistobeapplied.Anaction(e.g.,architecturaldesign)encompassesasetoftasksthatproduceamajorworkproduct(e.g.,anarchitecturaldesignmodel).Ataskfocusesonasmall,butwell-definedobjective(e.g.,conductingaunittest)thatproducesatangibleoutcome.2.1.2SoftwareProcessModelTherearelotsofsoftwareprocessmodels,including

waterfall,

prototyping,

iterative,incrementaldevelopment,

spiraldevelopment,

rapidapplicationdevelopment,

extremeprogramming

andvarioustypesof

agilemethodology.

ThewaterfallmodelTheIncrementalmodelTheSpiralmodelTheAgileprocessAvarietyofsoftwareprocessmodelshaveevolvedovertheyears,eachwithitsownrecognizedstrengthsandweaknesses.Onesoftwaredevelopmentprocessmodelisnotnecessarilysuitableforusebyallprojects.Eachoftheavailableprocessmodelisbestsuitedtospecifickindsofprojects,basedonvarioustechnical,organizationalandteamconsiderations.2.1.3PhasesofSoftwareDevelopmentSoftwaredevelopmentlifecycleSoftwaredevelopmentlifecycle,usuallyreferredtoasSDLC,isanoutlineofaprocessthathelpsdevelopsuccessfullysoftwaresystems.AnSDLCisasplittingofsoftwaredevelopmentworkintodistinctphase(orstages)containingactivitieswiththeintentofbetterplanningandmanagement.Thesephasesencompassplanning,analysis,design,implementationandmaintenancephases.Theimportantthingforconstructingasystemistohaveaplan.Theprocessofplanningandbuildinganapplicationsystemarecalledsystemsanalysisanddesign.Thisprocessbeginswithplanningphase.PlanningphaseAnalysisphaseDesignphaseImplementationphaseMaintenancephase1.PlanningphaseThegoalofthisperiodistocreateaprojectdevelopmentplan.So,theactivitiesincludedintheplanningphaseareshownasthefollowing:AssembletheprojectteamJustifyprojectChoosedevelopmentmethodologyDevelopaprojectscheduleProduceaprojectdevelopmentplan2.AnalysisphaseThegoaloftheanalysisphaseistoproducealistofrequirementsforaneworrevisedinformationsystem.Intheanalysisphase,theprojectteamdetermineswhatthenewsystemmustdo.Aseriesofactivitiesfortheanalysisphaseareshownasthefollowing:StudythecurrentsystemDeterminesystemrequirementsWriterequirementsreport

3.DesignphaseDuringthedesignphaseofSDLC,developersmustfigureouthowthenewsystemwillfulfilltherequirementsspecifiedinthesystemrequirementsreport.Tasksforthedesignphasearelistedinthefollowing:IdentifypotentialsolutionsEvaluatesolutionsandselectthebestSelecthardwareandsoftwareDevelopapplicationspecificationsObtainapprovaltoimplementthenewsystem

4.ImplementationphaseInimplementationphase,theprojectteamsupervisesthetasksnecessarytoconstructthenewsoftwaresystem.Thetasksthattakeplaceinthisphasecanincludeanyofthoseshowninthenext:Purchaseandinstallhardwareand/orsoftwareCreateapplicationsTestapplicationsFinalizedocumentationTrainusersConvertdataConverttonewsystem5.MaintenancephaseDuringthemaintenancephase,thegoalsareday-to-dayoperationofsystem,makingmodificationstoimproveperformance,andcorrectingproblems.Theactivitiesduringthephaseshouldensurethatthesystemfunctionsaswellaspossible.Themainactivitiesinvolvethefollowing:OperateequipmentMakebackupsProvidehelptousersFixbugsOptimizespeedandsecurityRevisesoftwareasnecessarytomeetbusinessneeds2.1.4MethodologyofSoftwareDevelopmentAsoftwaredevelopmentteamtypicallydevelopsasoftwaresystemaccordingtoaspecificmethodologyandasetofrelateddevelopmenttools.Thestructuredmethodologyandtheobject-orientedmethodologyarethetwodistinguishedmethodologiesinpractice.Thestructuredmethodologyisconsideredasthetypicalone.Itfocusesontheprocessesofasoftwaresystem.Theobject-orientedmethodologytreatsaninformationsystemasacollectionofobjectsthatinteractwitheachothertoaccomplishspecifictasks.191.Whatissoftwareengineering?2.Whatisasoftwareprocessmodel?Explaintherolesofsoftwareprocessmodelindevelopmentactivities.3.Howmanysoftwareprocessmodelshavebeendiscussedinthischapter?4.

Howmanyphasesarethereinthesoftwaredevelopmentlifecycle?Describethetasksofeachphase.ConceptCheck202.2SOFTWAREREENGINEERINGManysoftwaresystemstendtogrowlargerwithtime,andbecomelessstructuredwithchangesandlessunderstandablewithstuffturnover.Astheresult,theapplicationsbecomeunstable.Yettheapplicationsmustcontinuetoevolve.Ontheotherside,bothmaintenanceoftheinterfacesandtheimplementationhavenontrivialpercentagecostsoftheIT-budget.Whattodo?Infact,thebroadeningemphasisonsoftwarereengineeringhasbeenspawnedbysoftwaremaintenanceproblems.Reengineeringalegacysoftwaresystemtosupportnew,moderntechnologiesinsteadofoldonesisnotaneasytask,especiallyforlargesystemswithcomplexarchitecture.212.2SOFTWAREREENGINEERINGOriginofReengineeringASoftwareReengineeringModelSoftwareReengineeringActivities2.2.1OriginofReengineeringWhatisreengineering?Reengineering,alsoknownasbothrenovationandreclamation,is

theexaminationandalterationofasoftwaresystemtoreconstituteitinanewformandthesubsequentimplementationofthenewform.Theactivitiesofreengineeringgenerallyincludesinventoryanalysis,reverseengineering,forwardengineering,documentationrestructuring,coderestructuringanddatarestructuring.ThetwohistoricreengineeringinitiatorsTheY2Kproblem:Formanycompaniesthiswasthefirsttimetheyhadtodealwithreengineeringmechanisms.Y2Kalonecreatedamulti-billionreengineeringmarketandignitedtheoffshoresoftwareindustryinIndiaandothercountries.TheintroductionoftheEURO:TheintroductionoftheEUROcreatedanotherhugereengineeringrequest,mainlyintheEuropeanfinanceindustry.Twosignificantchangeshadtobeaddressednearlyatthesametime,theintroductionoftheEUROtobecompletedbyJanuary1,1999andtheY2KproblemtoberesolvedatlatestonJanuary1,2000.2.2.2ASoftwareReengineeringModelReengineeringisarebuildingactivity.Asoftwarereengineeringprocessmodeldefinessixactivities,showninFigure2-3.2.2.3SoftwareReengineeringActivitiesInventoryanalysisDocumentrestructuringReverseengineeringCoderestructuringDatarestructuringForwardengineering1.InventoryanalysisEverysoftwareorganizationshouldhaveaninventoryofallapplications.Theinventorycanbenothingmorethanaspreadsheetmodelcontaininginformationthatprovidesadetaileddescription(e.g.,size,age,businesscriticality)ofeveryactiveapplication.Bysortingthisinformationaccordingtobusinesscriticality,longevity,currentmaintainabilityandsupportability,andotherlocallyimportantcriteria,candidatesforreengineeringappear.Resourcescanthenbeallocatedtocandidateapplicationsforreengineeringwork.Itisimportanttonotethattheinventoryshouldberevisitedonaregularcycle.Thestatusofapplications(e.g.,businesscriticality)canchangeasafunctionoftime,andasaresult,prioritiesforreengineeringwillshift.2.DocumentrestructuringCreatingdocumentationisfartootimeconsuming.Ifthesystemworks,youmaychoosetolivewithwhatyouhave.Insomecases,thisisthecorrectapproach.Documentationmustbeupdated,butyourorganizationhaslimitedresources.You’llusea“documentwhentouched”approach.Itmaynotbenecessarytofullyredocumentanapplication.Rather,thoseportionsofthesystemthatarecurrentlyundergoingchangearefullydocumented.Overtime,acollectionofusefulandrelevantdocumentationwillevolve.Thesystemiscriticalbusinessandmustbefullyredocumented.Eveninthiscase,anintelligentapproachistoparedocumentationtoanessentialminimum.3.ReverseengineeringThetermreverseengineeringhasitsoriginsinthehardwareworld.Reverseengineeringforsoftwareisquitesimilar.Inmostcases,however,theprogramtobereverseengineeredisnotacompetitor’s.Rather,itisthecompany’sownwork(oftendonemanyyearsearlier).The“secrets”tobeunderstoodareobscurebecausenospecificationwaseverdeveloped.Therefore,reverseengineeringforsoftwareistheprocessofanalyzingaprograminanefforttocreatearepresentationoftheprogramatahigherlevelofabstractionthansourcecode.Reverseengineeringisaprocessofdesignrecovery.Reverseengineeringtoolsextractdata,architectural,andproceduraldesigninformationfromanexistingprogram.4.CoderestructuringThemostcommontypeofreengineering(actually,theuseofthetermreengineeringisquestionableinthiscase)iscoderestructuring.Somelegacysystemshavearelativelysolidprogramarchitecture,butindividualmoduleswerecodedinawaythatmakesthemdifficulttounderstand,test,andmaintain.Insuchcases,thecodewithinthesuspectmodulescanberestructured.Toaccomplishthisactivity,thesourcecodeisanalyzedusingarestructuringtool.Violationsofstructuredprogrammingconstructsarenotedandcodeisthenrestructured(thiscanbedoneautomatically)orevenrewritteninamoremodernprogramminglanguage.Theresultantrestructuredcodeisreviewedandtestedtoensurethatnoanomalieshavebeenintroduced.Internalcodedocumentationisupdated.5.DatarestructuringAprogramwithweakdataarchitecturewillbedifficulttoadaptandenhance.Infact,formanyapplications,informationarchitecturehasmoretodowiththelong-termviabilityofaprogramthanthesourcecodeitself.Datarestructuringisafull-scalereengineeringactivity.Inmostcases,datarestructuringbeginswithareverseengineeringactivity.Currentdataarchitectureisdissected,anddatamodelsaredefinedwhennecessary.Dataobjectsandattributesareidentified,andexistingdatastructuresarereviewedforquality.Whendatastructureisweak,thedataarereengineered.Becausedataarchitecturehasastronginfluenceonprogramarchitectureandthealgorithmsthatpopulateit,changestothedatawillinvariablyresultineitherarchitecturalorcode-levelchanges.6.ForwardengineeringForwardengineeringisthetraditionalprocessofmovingfromhigh-levelabstractionsandlogical,implementation-independentdesignstothephysicalimplementationofasystem.Forwardengineeringnotonlyrecoversdesigninformationfromexistingsoftwarebutusesthisinformationtoalterorreconstitutetheexistingsysteminanefforttoimproveitsoverallquality.Inmostcases,reengineeredsoftwarereimplementsthefunctionoftheexistingsystemandalsoaddsnewfunctionsand/orimprovesoverallperformance.ConceptCheckWhatissoftwarereengineering?Discussthetwotypicalreengineeringproblems.Whatkindsofactivitiesareincludedinasoftwarereengineeringmodel?Explainthemainreasonsthatmanycorporationsneedapragmaticstrategyforsoftwarereengineering.Discusstheroleofeachactivityincludedinasoftwarereengineeringmodel.332.3REVERSEENGINEERINGWhatisReverseEngineering?TheReverseEngineeringProcessReverseEngineeringtoUnderstandProcessingReverseEngineeringtoUnderstandDataReverseEngineeringUserInterfaces2.3.1WhatisReverseEngineering?Reverseengineeringistheprocessofanalyzingasubjectsystemto?Identifythesystem’scomponentsandtheirinterrelationships;?Createrepresentationsofthesysteminanotherformoratahigherlevelofabstraction.Reverseengineeringgenerallyinvolvesextractingdesignartifactsandbuildingorsynthesizingabstractionsthatarelessimplementation-dependent.Whilereverseengineeringofteninvolvesanexistingfunctionalsystemasitssubject,thisisnotarequirement.Youcanperformreverseengineeringstartingfromanylevelofabstractionoratanystageofthelifecycle.2.Keyobjectives1)Copewithcomplexity.2)Generatealternateviews.3)Recoverlostinformation.4)Detectsideeffects.5)Synthesizehigherabstractions.6)Facilitatereuse.2.3.2TheReverseEngineeringProcessInspanningthelife-cyclestages,reverseengineeringcoversabroadrangestartingfromtheexistingimplementation,recapturingorrecreatingthedesign,anddecipheringtherequirementsactuallyimplementedbythesubjectsystem.Therearemanysubareasofreverseengineering.Twosubareasthatarewidelyreferredtoareredocumentationanddesignrecovery.ThereverseengineeringprocessisrepresentedinFigure2-4.Beforereverseengineeringactivitiescancommence,unstructured(“dirty”)sourcecodeisrestructuredsothatitcontainsonlythestructuredprogrammingconstructs.Thismakesthesourcecodeeasiertoreadandprovidesthebasisforallthesubsequentreverseengineeringactivities.Thecoreofreverseengineeringisanactivitycalledextractabstractions.Youmustevaluatetheoldprogramandfromthe(oftenundocumented)sourcecode,developameaningfulspecificationoftheprocessingthatisperformed,theuserinterfacethatisapplied,andtheprogramdatastructuresordatabasethatisused.

Figure2-4Thereverseengineeringprocess2.3.3ReverseEngineeringtoUnderstandProcessingReverseengineeringtounderstandprocessingbeginswithanattempttounderstandandthenextractproceduralabstractionsrepresentedbythesourcecode.Tounderstandproceduralabstractions,thecodeisanalyzedatvaryinglevelsofabstraction:system,program,component,pattern,andstatement.Theoverallfunctionalityoftheentireapplicationsystemmustbeunderstoodbeforemoredetailedreverseengineeringworkoccurs.Thisestablishesacontextforfurtheranalysisandprovidesinsightintointeroperabilityissuesamongapplicationswithinthesystem.2.3.4ReverseEngineeringtoUnderstandDataReverseengineeringofdataoccursatdifferentlevelsofabstractionandisoftenthefirstreengineeringtask.Attheprogramlevel,internalprogramdatastructuresmustoftenbereverseengineeredaspartofanoverallreengineeringeffort.Atthesystemlevel,globaldataareoftenreengineeredtoaccommodatenewdatabasemanagementparadigms.Reverseengineeringofthecurrentglobaldatastructuressetsthestagefortheintroductionofanewsystem-widedatabase.2.3.4ReverseEngineeringtoUnderstandDataDatabasereengineering,consistsoftransformingalegacydatabaseaccordingtonewtechnicalrequirements,whilekeepingtheinformationcontentsunchanged.Substitutingamoderndatamanagementsystem(relationalDBMSforinstance)foranoutdatedmanager(typicallystandardfilemanager),orimprovingthelogicalschematogainbetterperformancearepopularscenarios.Regardlessofitslogicalorganizationandphysicalstructure,adatabaseallowsthedefinitionofdataobjectsandsupportssomemethodforestablishingrelationshipsamongtheobjects.Therefore,reengineeringonedatabaseschemaintoanotherrequiresanunderstandingofexistingobjectsandtheirrelationships.2.3.4ReverseEngineeringtoUnderstandDataTypically,theprocessthatconvertingalegacysystemtoamoderndatabasetechnology,comprisesthefollowingthreemainsteps:(1)Databaseschemaconversion:thelegacydatabaseschemaistranslatedintoanequivalentschemaexpressedinthetargettechnology.(2)Dataconversion:thedatabasecontentsaremigratedfromthelegacydatabasetothenewone.Thisstepconsistsofaschema-drivenETLprocess.(3)Programconversion:thelegacyprogramsaremodifiedsothattheyaccessthenewdatabaseinsteadofthelegacydata.Inthescenariostudied,thefunctionalities,theprogramminglanguageandtheuserinterfacearekeptunchanged.Thisconversionstepisgenerallyacomplexproce