软件工程第9版部分习题答案Word格式.doc

软件工程第9版部分习题答案Word格式.doc

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1.3Whatarethefourimportantattributesthatallprofessionalsoftwareshouldhave?

Suggestfourotherattributesthatmaysometimesbesignificant.

Answer:

Fourimportantattributesaremaintainability,dependability,performanceandusability.Otherattributesthatmaybesignificantcouldbereusability（canitbereusedinotherapplications）,distributability（canitbedistributedoveranetworkofprocessors）,portability（canitoperateonmultipleplatformse.glaptopandmobileplatforms）andinter-operability（canitworkwithawiderangeofothersoftwaresystems）.

Decompositionsofthe4keyattributese.g.dependabilitydecomposestosecurity,safety,availability,etc.isalsoavalidanswertothisquestion.

2.1

Givingreasonsforyouranswerbasedonthetypeofsystembeingdeveloped,suggestthemostappropriategenericsoftwareprocessmodelthatmightbeusedasabasisformanagingthedevelopmentofthefollowingsystems:

•Asystemtocontrolanti-lockbrakinginacar

•Avirtualrealitysystemtosupportsoftwaremaintenance

•Auniversityaccountingsystemthatreplacesanexistingsystem

•Aninteractivetravelplanningsystemthathelpsusersplanjourneyswiththelowestenvironmentalimpact

1.Anti-lockbrakingsystemThisisasafety-criticalsystemsorequiresalotofup-frontanalysisbeforeimplementation.Itcertainlyneedsaplan-drivenapproachtodevelopmentwiththerequirementscarefullyanalysed.Awaterfallmodelisthereforethemostappropriateapproachtouse,perhapswithformaltransformationsbetweenthedifferentdevelopmentstages.

2.VirtualrealitysystemThisisasystemwheretherequirementswillchangeandtherewillbeanextensiveuserinterfacecomponents.Incrementaldevelopmentwith,perhaps,someUIprototypingisthemostappropriatemodel.Anagileprocessmaybeused.

3.UniversityaccountingsystemThisisasystemwhoserequirementsarefairlyell-knownandwhichwillbeusedinanenvironmentinconjunctionwithlotsofotherstemssuchasaresearchgrantmanagementsystem.Therefore,areuse-basedproachislikelytobeappropriateforthis.

4.InteractivetravelplanningsystemSystemwithacomplexuserinterfacebutwhichmustbestableandreliable.Anincrementaldevelopmentapproachisthemostappropriateasthesystemrequirementswillchangeasrealuserexperiencewiththesystemisgained.

2.4

Suggestwhyitisimportanttomakeadistinctionbetweendevelopingtheuserrequirementsanddevelopingsystemrequirementsintherequirementsengineeringprocess.

Thereisafundamentaldifferencebetweentheuserandthesystemrequirementsthatmeantheyshouldbeconsideredseparately.

1.Theuserrequirementsareintendedtodescribethesystem’sfunctionsandfeaturesfromauserperspectiveanditisessentialthatusersunderstandtheserequirements.Theyshouldbeexpressedinnaturallanguageandmaynotbeexpressedingreatdetail,toallowsomeimplementationflexibility.Thepeopleinvolvedintheprocessmustbeabletounderstandtheuser’senvironmentandapplicationdomain.

2.Thesystemrequirementsaremuchmoredetailedthantheuserrequirementsandareintendedtobeaprecisespecificationofthesystemthatmaybepartofasystemcontract.Theymayalsobeusedinsituationswheredevelopmentisoutsourcedandthedevelopmentteamneedacompletespecificationofwhatshouldbedeveloped.Thesystemrequirementsaredevelopedafteruserrequirementshavebeenestablished.

Excercises（Homework）:

P116

4.2，*4.4

4.2

Discoverambiguitiesoromissionsinthefollowingstatementofrequirementsforpartofaticket-issuingsystem:

Anautomatedticket-issuingsystemsellsrailtickets.Usersselecttheirdestinationandinputacreditcardandapersonalidentificationnumber.

Therailticketisissuedandtheircreditcardaccountcharged.Whentheuserpressesthestartbutton,amenudisplayofpotentialdestinationsisactivated,alongwithamessagetotheusertoselectadestination.Onceadestinationhasbeenselected,usersarerequestedtoinputtheircreditcard.

Itsvalidityischeckedandtheuseristhenrequestedtoinputapersonalidentifier.Whenthecredittransactionhasbeenvalidated,theticketisissued.

Ambiguitiesandomissionsinclude:

l•Canacustomerbuyseveralticketsforthesamedestinationtogetherormusttheybeboughtoneatatime?

l•Cancustomerscancelarequestifamistakehasbeenmade?

l•Howshouldthesystemrespondifaninvalidcardisinput?

l•Whathappensifcustomerstrytoputtheircardinbeforeselectingadestination（astheywouldinATMmachines）?

l•Musttheuserpressthestartbuttonagainiftheywishtobuyanothertickettoadifferentdestination?

l•Shouldthesystemonlysellticketsbetweenthestationwherethemachineissituated