计算机科学概论(第9版)Lecture_slide07.ppt

SoftwareEngineering Chapter7 fromtextbook WhySoftwareEngineering Softwaredevelopmentishard Importanttodistinguish easy systems onedeveloper oneuser experimentaluseonly from hard systems multipledevelopers multipleusers products Experiencewith easy systemsismisleadingOnepersontechniquesdonotscaleupAnalogywithbridgebuilding Overastream easy onepersonjobOverRiverSevern thetechniquesdonotscale WhySoftwareEngineering TheproblemiscomplexityManysources butsizeiskey UNIXcontains4millionlinesofcodeWindows2000contains108linesofcodeSoftwareengineeringisaboutmanagingthiscomplexity RecommendedCourseTextbooks SommervilleI 2001 2004 SoftwareEngineering6thor7thEdition Addison Wesley Harlow Essex UKStevensP withPooley R 2000 UsingUML SoftwareEngineeringwithObjectsandComponents Addison Wesley Harlow Essex UKIntroducingAsml 2001 Microsoftcorporation Sommerville StevensBundle FAQsaboutsoftwareengineering Whatissoftware softwareprocess softwareengineering softwareprocessmodel Whatissoftwareengineering Whatisthedifferencebetweensoftwareengineeringandcomputerscience betweensoftwareengineeringandsystemengineering Whatissoftware ComputerprogramsandassociateddocumentationSoftwareproductsmaybedevelopedforaparticularcustomerormaybedevelopedforageneralmarketSoftwareproductsmaybeGeneric developedtobesoldtoarangeofdifferentcustomersBespoke custom developedforasinglecustomeraccordingtotheirspecification Whatissoftwareengineering SoftwareengineeringisanengineeringdisciplinewhichisconcernedwithallaspectsofsoftwareproductionSoftwareengineersshouldadoptasystematicandorganisedapproachtotheirworkuseappropriatetoolsandtechniquesdependingontheproblemtobesolved thedevelopmentconstraintsandtheresourcesavailable Whatisthedifferencebetweensoftwareengineeringandcomputerscience ComputerScience SoftwareEngineering isconcernedwith Computersciencetheoriesarecurrentlyinsufficienttoactasacompleteunderpinningforsoftwareengineering BUTitisafoundationforpracticalaspectsofsoftwareengineering Whatisthedifferencebetweensoftwareengineeringandsystemengineering SoftwareengineeringispartofSystemengineeringSystemengineeringisconcernedwithallaspectsofcomputer basedsystemsdevelopmentincludinghardware softwareandprocessengineeringSystemengineersareinvolvedinsystemspecification architecturaldesign integrationanddeployment Whatisasoftwareprocess AsetofactivitieswhosegoalisthedevelopmentorevolutionofsoftwareGenericactivitiesinallsoftwareprocessesare Specification whatthesystemshoulddoanditsdevelopmentconstraintsDevelopment productionofthesoftwaresystemValidation checkingthatthesoftwareiswhatthecustomerwantsEvolution changingthesoftwareinresponsetochangingdemands Whatisasoftwareprocessmodel Asimplifiedrepresentationofasoftwareprocess presentedfromaspecificperspectiveExamplesofprocessperspectives Workflowperspectiverepresentsinputs outputsanddependenciesData flowperspectiverepresentsdatatransformationactivitiesRole actionperspectiverepresentstheroles activitiesofthepeopleinvolvedinsoftwareprocessGenericprocessmodelsWaterfallEvolutionarydevelopmentFormaltransformationIntegrationfromreusablecomponents WaterfallModel Thespiralmodel ThespiralmodelbyB Boehm 1980 isamoresophisticatedextensionofthewaterfallmodel http en wikipedia org wiki Spiral model Thespiralmodeldescribesrepeatingphasesofobjectivedetermination riskidentification developmentandtest andfinallyplanningofthenextiteration Ateachiteration anewprototypeisdesignedwhereeachhasmoredetailthanitspredecessor ITERATIVEMODEL ReviewQ Whatistheroleofasoftwarerequirementsspecificationdocument Summerizeeachof4stageswithinthedevelopmentphaseofthesoftwarelifecycle Whatarethecostsofsoftwareengineering Roughly60 ofcostsaredevelopmentcosts 40 aretestingcosts Forcustomsoftware evolutioncostsoftenexceeddevelopmentcostsCostsvarydependingonthetypeofsystembeingdevelopedandtherequirementsofsystemattributessuchasperformanceandsystemreliabilityDistributionofcostsdependsonthedevelopmentmodelthatisused WhatisCASE Computer AidedSoftwareEngineering Upper CASEToolstosupporttheearlyprocessactivitiesofrequirementsanddesignLower CASEToolstosupportlateractivitiessuchasprogramming debuggingandtesting Softwaresystemswhichareintendedtoprovideautomatedsupportforsoftwareprocessactivities suchasrequirementsanalysis systemmodelling debuggingandtesting Whataretheattributesofgoodsoftware MaintainabilitySoftwaremustevolvetomeetchangingneedsDependabilitySoftwaremustbetrustworthyEfficiencySoftwareshouldnotmakewastefuluseofsystemresourcesUsabilitySoftwaremustbeusablebytheusersforwhichitwasdesigned Thesoftwareshoulddelivertherequiredfunctionalityandperformancetotheuserandshouldbemaintainable dependableandusable Whatarethekeychallengesfacingsoftwareengineering Softwareengineeringinthe21stcenturyfacesthreekeychallenges LegacysystemsOld valuablesystemsmustbemaintainedandupdatedHeterogeneitySystemsaredistributedandincludeamixofhardwareandsoftwareDeliveryThereisincreasingpressureforfasterdeliveryofsoftware Professionalandethicalresponsibility SoftwareengineeringinvolveswiderresponsibilitiesthansimplytheapplicationoftechnicalskillsSoftwareengineersmustbehaveinanhonestandethicallyresponsiblewayiftheyaretoberespectedasprofessionalsEthicalbehaviourismorethansimplyupholdingthelaw Issuesofprofessionalresponsibility ConfidentialityEngineersshouldnormallyrespecttheconfidentialityoftheiremployersorclientsirrespectiveofwhetherornotaformalconfidentialityagreementhasbeensigned CompetenceEngineersshouldnotmisrepresenttheirlevelofcompetence Theyshouldnotknowinglyacceptworkwhichisoutwiththeircompetence Issuesofprofessionalresponsibility IntellectualpropertyrightsEngineersshouldbeawareoflocallawsgoverningtheuseofintellectualpropertysuchaspatents copyright etc Theyshouldbecarefultoensurethattheintellectualpropertyofemployersandclientsisprotected ComputermisuseSoftwareengineersshouldnotusetheirtechnicalskillstomisuseotherpeople scomputers Computermisuserangesfromrelativelytrivial gameplayingonanemployer smachine say toextremelyserious disseminationofviruses ACM IEEECodeofEthics TheprofessionalsocietiesintheUShaveco operatedtoproduceacodeofethicalpractice Membersoftheseorganisationssignuptothecodeofpracticewhentheyjoin TheCodecontainseightPrinciplesrelatedtothebehaviourofanddecisionsmadebyprofessionalsoftwareengineers includingpractitioners educators managers supervisorsandpolicymakers aswellastraineesandstudentsoftheprofession Codeofethics principles 1 PUBLICSoftwareengineersshallactconsistentlywiththepublicinterest 2 CLIENTANDEMPLOYERSoftwareengineersshallactinamannerthatisinthebestinterestsoftheirclientandemployerconsistentwiththepublicinterest 3 PRODUCTSoftwareengineersshallensurethattheirproductsandrelatedmodificationsmeetthehighestprofessionalstandardspossible Codeofethics principles 4 JUDGMENTSoftwareengineersshallmaintainintegrityandindependenceintheirprofessionaljudgement 5 MANAGEMENTSoftwareengineeringmanagersandleadersshallsubscribetoandpromoteanethicalapproachtothemanagementofsoftwaredevelopmentandmaintenance 6 PROFESSIONSoftwareengineersshalladvancetheintegrityandreputationoftheprofessionconsistentwiththepublicinterest Codeofethics principles 7 COLLEAGUESSoftwareengineersshallbefairtoandsupportiveoftheircolleagues 8 SELFSoftwareengineersshallparticipateinlifelonglearningregardingthepracticeoftheirprofessionandshallpromoteanethicalapproachtothepracticeoftheprofession Keypoints Softwareengineeringisanengineeringdisciplinewhichisconcernedwithallaspectsofsoftwareproduction Softwareproductsconsistofdevelopedprogramsandassociateddocumentation Essentialproductatt