软件工程第9版部分习题答案

精品文档习题参考答案Exercises(Homework):P251.3Whatarethefourimportantattributesthatprofessional谢谢阅读softwareshouldhave?Suggestfourotherattributesthatmaysometimesbesignificant.精品文档放心下载Fourimportantattributesaremaintainability,dependability,

performanceandusability.Otherattributesthatmaybesignificantcouldreusability(canitbereusedinotherapplications),distributability(canitbedistributedanetworkofprocessors),portability(canitoperate

onmultipleplatformse.glaptopmobileplatforms)inter-operability

(canwitharangeothersoftwaresystems).精品文档放心下载Decompositionsofthe4keyattributese.g.dependabilitydecomposesto

security,safety,availability,etc.isavalidanswertothis

question.感谢阅读2.1Givingreasonsforbasedthetypedeveloped,suggestthemostappropriategenericsoftwaremodelthat

mightbeusedasabasisformanagingthedevelopmentofthefollowing

systems:感谢阅读•Asystemtocontrolanti-lockbrakinginacar感谢阅读•Avirtualrealitysystemtosoftwaremaintenance

•Auniversityaccountingsystemthatreplacesexistingsystem

•Aninteractivetravelplanningsystemthathelpsusersplanjourneys

thelowestenvironmentalimpact精品文档放心下载谢谢阅读精品文档放心下载1.Anti-lockbrakingsystemThisisasafety-criticalsystemsorequires

aofup-frontanalysisbeforeimplementation.Itcertainlyneedsa

plan-drivenapproachtodevelopmenttherequirementscarefully

analysed.Awaterfallmodelisthereforethemostappropriateapproach

toperhapsformaltransformationsbetweenthedifferent

developmentstages.谢谢阅读精品文档放心下载谢谢阅读2.VirtualrealitysystemThisisasystemwheretherequirementswill

changetherewillanextensiveuserinterfacecomponents.

Incrementaldevelopmentwith,someUIprototypingisthemost

appropriatemodel.Anagileprocessmaybeused.精品文档放心下载UniversityaccountingsystemThisisasystemwhoserequirementsare

fairlyell-knownwhichwillbeusedinenvironmentinconjunctionwithlotsof

otherstemssuchasaresearchgrantmanagementsystem.精品文档放心下载Therefore,areuse-basedproachislikelytobeappropriateforthis.

InteractivetravelplanningsystemSystemacomplex精品文档放心下载谢谢阅读1欢迎下载。精品文档interfacewhichmuststableandreliable.Anincremental

developmentapproachisthemostappropriateasthesystemrequirements

changeasuserexperiencethesystemisgained.精品文档放心下载感谢阅读谢谢阅读2.4Suggestwhyitisimportanttomakeadistinctionbetweendevelopingtheuserrequirementsanddevelopingsystemrequirementsintherequirementsengineeringprocess.感谢阅读精品文档放心下载Thereisafundamentaldifferencebetweentheuserandthesystem

requirementsthattheyshouldbeconsideredseparately.

1.Theuserrequirementsareintendedtodescribethesystem’s

functionsfeaturesfromaperspectiveitisessentialthatusers

understandtheserequirements.Theyshouldexpressedinnatural

languageandmaybeexpressedingreattoallowsome

implementationflexibility.Thepeopleinvolvedintheprocessmustbeableto

understandtheuser’senvironmentandapplicationdomain.感谢阅读精品文档放心下载感谢阅读谢谢阅读2.Thesystemrequirementsaremuchmoredetailedthantheuser

requirementsareintendedtoaprecisespecificationthesystem

thatmaypartasystemcontract.Theymayalsousedinsituationswhere

developmentisoutsourcedandthedevelopmentteamneedacomplete

specificationofshouldbedeveloped.Thesystemrequirementsare

developedafteruserrequirementshavebeenestablished.感谢阅读Excercises(Homework):P116精品文档放心下载4.2，4.2Discoverambiguitiesomissionsinthefollowingstatementof

requirementsforpartofaticket-issuingsystem:

Anautomatedticket-issuingsystemsellsrailtickets.Usersselecttheir

destinationandacreditcardandapersonalidentification

number.精品文档放心下载精品文档放心下载精品文档放心下载Therailticketisissuedandtheircreditcardaccountcharged.When

theuserpressesthestartbutton,amenudisplaypotentialdestinationsis

activated,alongamessagetothetoselect精品文档放心下载adestination.Onceadestinationbeenselected,usersarerequested

totheircreditcard.精品文档放心下载精品文档放心下载Itsischeckedandtheisthenrequestedtoinputa

personalidentifier.Whenthecredittransactionbeenvalidated,the

ticketis感谢阅读精品文档放心下载Ambiguitiesandomissionsinclude:精品文档放心下载2欢迎下载。精品文档•acustomerseveralticketsforthesamedestinationtogether精品文档放心下载ormusttheybeboughtoneatatime?精品文档放心下载•customerscancelaifamistakebeenmade?

•shouldthesystemrespondifaninvalidcardisinput?

•Whathappensifcustomerstrytotheircardinbeforeselecting

adestination(astheywouldinATMmachines)?感谢阅读感谢阅读•Musttheuserpressthestartbuttonagainiftheywishtobuyanother感谢阅读tickettoadifferentdestination?感谢阅读•Shouldthesystemsellticketsbetweenthestationwherethe

machineissituatedanddirectconnectionsorshoulditincludeall

possibledestinations?谢谢阅读感谢阅读4.4Writeasetnon-functionalrequirementstheticket-issuing

system,settingitsexpectedreliabilityandresponsetime.感谢阅读精品文档放心下载Possiblenon-functionalrequirementsfortheticketsystem

include:谢谢阅读1.Between0600and2300inanyoneday,thetotalsystemdowntimeshould

exceed5minutes.谢谢阅读Between06002300inanyday,therecoverytimeafterasystem

failureshouldnotexceed2minutes.精品文档放心下载谢谢阅读3.Between2300and0600inanyoneday,thetotalsystemdowntimeshould

exceed20minutes.感谢阅读Alltheseareavailabilityrequirements–thatthesevary

accordingtothetimeday.Failureswhenmostpeoplearetravelingare

acceptablethanfailureswhentherearefewcustomers.

4.Afterthecustomerpressesabuttononthemachine,thedisplayshould

beupdatedwithinseconds.精品文档放心下载感谢阅读感谢阅读精品文档放心下载感谢阅读Theticketissuingtimeaftercreditcardvalidationhasreceivedshouldexceed10seconds.感谢阅读精品文档放心下载6.Whenvalidatingcreditcards,thedisplayshouldprovideastatus

messageforcustomersindicatingthatactivityistakingplace.Thistells

thecustomerthatthepotentiallytimeconsumingactivityofvalidation

isstillinprogressthatthesystemnotsimplyfailed.

7.Themaximumacceptablefailurerateforticketissuerequestsis1:精品文档放心下载精品文档放心下载感谢阅读感谢阅读Excercises(Homework):P143-144精品文档放心下载5.2，5.5，5.6，5.75.2mightyouuseamodelofasystemthatexists?Explain感谢阅读3欢迎下载。精品文档itisnecessaryforsuchasystemmodeltobecompleteand

correct.Wouldthesamebetrueifyouweredevelopingamodelofasystem?谢谢阅读精品文档放心下载mightcreateuseamodelofasystemthatalreadyexistsfor

thefollowing谢谢阅读1.Tounderstandanddocumentthearchitectureandoperationthe

existing感谢阅读system.2.Toasthefocusofdiscussionpossiblechangestothat

system.精品文档放心下载3.Toinformthere-implementationthesystem.精品文档放心下载notneedacompletemodelunlesstheintentionistocompletely

documenttheoperationoftheexistingsystem.Theaimofthemodelinsuch

casesisusuallytohelpyouworkpartsthesystemsoonlytheseneedtobe

modelled.Furthermore,ifthemodelisusedasadiscussion

focus,youareunlikelytobeinterestedindetailsandsocanignorepartsofthesystem

inthemodel.感谢阅读Thisistrue,inforsystemsamodel-based

approachtodevelopmentistakingplaceinwhichcaseacompletemodelis

required.Theothercircumstanceswhereyoumayneedacompletemodel

iswhenthereisacontractualrequirementforsuchamodeltobeproducedasofthesystemdocumentation.感谢阅读感谢阅读5.5Developasequencediagramshowingtheinteractionsinvolvedwhena

studentregistersforacourseinauniversity.mayhavelimitedenrolment,

sotheregistrationprocessmustincludechecksthatareavailable.

Assumethatthestudentaccessesanelectroniccoursecatalogtofindaboutavailablecourses.感谢阅读Arelativelysimplediagramisallthatisneededhere.Itisbestnot

tobetoofussyaboutthingslikeUMLarrowstylesashardlyanyonecan

rememberthedifferencesbetweenthem.精品文档放心下载4欢迎下载。精品文档5.6carefullyatmessagesmailboxesarerepresentedintheemailsystem

thatyouuse.Modeltheobjectclassesthatmightbeusedinthe

systemimplementationtorepresentamailboxane-mailmessage.

谢谢阅读5.7BasedonyourexperiencewithabankATM,anactivitydiagramthat

modelsthedataprocessinginvolvedwhenacustomerwithdrawscashfromthe

machine.谢谢阅读5欢迎下载。精品文档NoticethatIhavenotdevelopedtheactivitiesrepresentingother

servicesfailedauthentication.感谢阅读Excercises(Homework):P173-1746.1,6.3,6.9精品文档放心下载6.1Whendescribingasystem,explainwhyyoumayhavetodesignthesystem

architecturebeforetherequirementsspecificationiscomplete.精品文档放心下载Thearchitecturemaytobedesignedbeforespecificationsarewritten

toprovideameansofstructuringthespecificationanddevelopingdifferentsubsystemspecificationsconcurrently,toallowmanufactureofhardware

bysubcontractorstoprovideamodelforsystemcosting.精品文档放心下载6.3Explaindesignconflictsmightarisewhendesigningarchitecture

forwhichbothavailabilityandsecurityrequirementsarethemostimportant

non-functionalrequirements.感谢阅读Fundamentally,toavailability,youneedtohave(a)replicated

componentsinthearchitecturesothatintheeventofonecomponent

failing,youcanswitchimmediatelytoabackupcomponent.Youalsoneedto

severalcopiesthedatathatisprocessed.Security

requiresminimizingthenumberofthedataand,whereverpossible,

adoptinganarchitecturewhereeachcomponentonlyknowsasmuch

asitneedsto,todoitsjob.Thisthechanceintruders感谢阅读感谢阅读谢谢阅读6欢迎下载。精品文档accessingthedata.Therefore,thereisafundamentalarchitecturalconflictbetween谢谢阅读availability(replication,severalcopies)andsecurity(specialization,谢谢阅读minimalcopies).Thesystemarchitecttofindthebestcompromisebetweenthesefundamentallyopposingrequirements.谢谢阅读谢谢阅读6.9UsingthebasicmodelofaninformationsystempresentedinFigure6.16,suggestthecomponentsthatmightbepartinformationsystem

that谢谢阅读allowsuserstoviewinformationaboutflightsarrivinganddeparting

fromaparticularairport.感谢阅读谢谢阅读Studentsshouldconsiderthelevelsintheinformationsystemandshould

identifycomponentsthatmightbeincludedatlevel.Examplesofthese

components谢谢阅读mightLevel1(Databaselevel)Flightdatabase;Flightstatusdatabase;Airportinformation;

Level2:(Informationretriev