软件工程课后习题答案

1、PAGE PAGE 17软件工程课课后习题答答案Chaptter1The ddefinnitioon foor sooftwaare ppreseentedd in Secttion 1.2 appllies to tthe WWeb ssitess. Thhere are, howweverr, suubtlee difffereencess bettweenn a WWeb ssite and convventiionall sofftwarre. Amonng thhe moost iimporrtantt aree thaat thhe coontennt thhat aa Webb

2、sitte prresennts iis coonsidderedd to be ppart of tthe WWeb AAppliicatiion wwhilee thaat daata pproceessedd by convventiionall sofftwarre iss oftten cconsiidereed too be sepaaratee froom thhe prrocesssingg funnctioons ddelivveredd.Who wwouldd havve thhoughht thhat ssoftwware woulld leead tto: (1) aa

3、 chaange in tthe ddatinng haabitss of manyy youung ppeoplle (IInterrnet datiing); (2) thee wayy peoople commmuniccate (celll phhoness); (3) mmethoods oof waarfarre (ccyberrweappons); (44) thhe diiagnoosis of ddiseaases (MRIIs annd reelateed coomputter-bbasedd diaagnosstic deviices), annd (55) thhe m

4、aannerr in whicch peeoplee acqquiree andd enjjoy mmediaa (muusic, DVDDs, eetc.).The LLaw oof Coonserrvatiion oof Faamiliiaritty: AAs thhe syystemm evoolvess thee useers eenginneerss, deevelooperss alll thoose aassocciateed muust hhave the comppletee knoowleddge oof thhe coontennt annd beehaviior tto

5、 acchievve saatisffactoory rresullts. Incrreasee in growwth mmay ddiminnish thatt knoowleddge (masttery); heence the averrage incrreasee in growwth rremaiins iinvarriantt as the systtem eevolvves.Many modeern aappliicatiions channge ffrequuentlly beeforee theey arre prresennted to tthe eend uuser an

6、d thenn aftter tthe ffirstt verrsionns haave bbeen usedd. A few wayss to builld sooftwaare tto sttop ddeterrioraationn duee to channge wwouldd be: Make suree thaat sooftwaare iis deesignned sso thhat cchangges iin onne paart oof a proggram do nnot ccreatte siide-eeffeccts iin annotheer paart oof thh

7、e prrograam.Make suree thaat sooftwaare iis deesignned sso thhat iit dooes nnot ddepennd onn extternaal deevicees orr sysstemss thaat arre liikelyy to channge wwith timee.Make suree tesst caases and resuults are archhivedd andd avaailabble sso thhat tthe ssoftwware can be rretessted whenn chaangess

8、aree madde.Make suree youu speend ttime undeerstaandinng whhat tthe ccustoomer wantts.The ttwo bbroaddest cateegoriies eencommpasss rissks aassocciateed wiith eeconoomic losss andd rissks tto thhe weell bbeingg of peopple. It mmightt be a goood iidea to sselecct fiive rriskss (cuulledd froom thhe so

9、ourcees nooted) andd preesentt theem too thee claass. Lookk forr hummorouus ass welll ass serriouss rissks.The ssame apprroachh to softtwaree enggineeeringg cann be appllied for eachh of the six cateegoriies, but it mmust be aadaptted tto acccommmodatte thhe sppeciaal reequirremennts oof eaach ccate

10、ggory. Theree aree litterallly ddozenns off reaal liife ccircuumstaancess to chooose ffrom. Forr exaamplee, sooftwaare eerrorrs thhat hhave caussed mmajorr tellephoone nnetwoorks to ffail, faiilurees inn aviioniccs thhat hhave conttribuuted to pplanee craashess, coomputter vvirusses (e.g., Miichella

11、ngeelo) thatt havve caausedd siggnifiicantt ecoonomiic loossess andd atttackss on majoor e-commmercee sittes.The LLaw oof Deeclinning Quallity: Thee quaalityy of systtems willl decclinee unlless theyy aree maiintaiined by vvarioous pproceedurees too adaapt tto thhe ennviroonmenntal channges. Thiis c

12、oonceppt iss simmilarr to the “detteriooratiion” disccusseed inn Prooblemm 1-55.The LLaw oof Coonserrvatiion oof Orrganiizatiionall Staabiliity: The averrage effeectivve glloball acttivitty raate iis innvariiant overr thee liffetimme off a pproduuct.Chaptter 222.1)Patteern: CommmuniccatioonIntennt:T

13、o eestabblishh a ccollaaboraativee rellatioonshiip wiith tthe ccustoomer in aan efffortt to defiine pprojeect sscopee, buusineess rrequiiremeents and otheer prrojecct coonstrraintts.” Type: Stagge paatterrnInitiial cconteext: (1) Apprropriiate stakkehollderss havve beeen iidenttifieed annd arre wiil

14、linng too parrticiipatee in commmuniccatioon (22) Sttakehholdeers aagreee thaat a probblem exissts aand tthat softtwaree mayy proovidee a ssoluttion Probllem: Requuiremmentss musst bee eliiciteed frrom sstakeeholdders and orgaanizeed inn a wway tthat can be uused by ssoftwware engiineerrs. AAll ssta

15、keeholdders mustt colllabooratee to defiine rrequiiremeents and to iidenttify thosse arreas wherre reequirremennts aare uuncerrtainn.Soluttion:Eachh staakehoolderr musst deeveloop a desccripttion of tthe ffuncttionss, feeaturres, infoormattion and behaaviorr thaat arre exxhibiited by tthe ssoftwware

16、. To accoompliish tthis, a sstrucctureed, ffacillitatted meetting is cconduuctedd. Foor moore ddetaiils, see Secttionss 7.33, 7.4 annd 7.5.Resulltingg Conntextt:Whenn thiis paatterrn haas beeen ssucceessfuully comppleteed, bbasicc infformaationn reqquireed foor thhe deeveloopmennt off an anallysiss

17、moddel hhas bbeen acquuiredd andd doccumennted in ssome mannner. Use-casees (uuser scennarioos) hhave beenn devvelopped, alonng wiith bbasicc desscripptionns off sysstem funcctionn andd behhavioor annd thhe daata oobjeccts tthat are to bbe maanipuulateed annd/orr prooduceed/Relatted PPatteerns: Conn

18、ductted aa meeetingg; reequirremennt gaatherring; devvelopping use-casees; bbuildding a miini-sspec; neggotiaatingg reqquireementts, ppriorritizzatioon. Knowwn Usses/EExampples: Commmuniicatiion iis maandattory at tthe bbeginnningg of everry sooftwaare pprojeect; is rrecommmendded tthrouughouut thhe

19、 sooftwaare pprojeect; and is mmandaatoryy oncce thhe deeployymentt acttivitty iss undderwaay.2.2) Proccess asseessmeent eexamiines the softtwaree proocesss useed byy an orgaanizaationn to deteerminne whhetheer itt is effeectivve inn achhieviing ssoftwware engiineerring goalls. The asseessmeent ccha

20、raacterrizess thee currrentt praacticce wiithinn an orgaanizaationnal uunit in ttermss of the capaabiliity oof thhe seelectted pproceessess. Thhe SPPICE (ISOO/IECC155004) sstanddard defiines a seet off reqquireementts foor sooftwaare pproceess aassesssmennt. TTo acccompplishh thee asssessmment, SPII

21、CE sspeciifiess a “refeerencce moodel” thaat exxaminnes tthe ppurpoose aand mmeasuurablle obbjecttivess of the proccess (thee “prrocesss diimenssion”) annd thhe seet off proocesss atttribuutes thatt shoould be ppreseent (the “cappabillity dimeensioon”).2.4) TTask Set for Commmuniccatioon Acctiviity:

22、 A taask sset wwouldd deffine the actuual wwork to bbe doone tto acccompplishh thee objjectiives of aa sofftwarre enngineeerinng acctionn. Foor thhe coommunnicattion actiivityy theese aare: Make a liist oof sttakehholdeers ffor tthe pprojeectInvitte alll thhe sttakehholdeers tto ann infformaal meeet

23、inngAsk tthem to mmake a liist oof feeaturres aand ffuncttionssDiscuuss rrequiiremeents and builld a finaal liistPriorritizze reequirremennts aand nnote the areaas thhat sstakeeholdders are unceertaiin offThesee tassks mmay bbe exxpandded ffor aa commplexx sofftwarre prrojecct, tthey may thenn conns

24、ideer thhe foollowwing: To coonducct a seriies oof sppecifficattion meettingss, buuild a prrelimminarry liist oof fuunctiions and featturess bassed oon sttakehholdeer innput.To buuild a reeviseed liist oof sttake holdder rrequiiremeents use quallity funcctionn depploymment techhniquues tto prriotiiz

25、e tthe rrequiiremeents.Note consstraiints and resttricttionss on the systtem.Discuuss mmethoods ffor vvaliddatinng syystemm.2.5)The CMMII reppreseents a prrocesss meetamoodel in 22 difffereent wwaysthe conttinuoous aand tthe sstageed moodel. Thee proos off thee CMMMI: ccomprrehennsivee, adddresssing

26、g virrtuallly eeveryy asppect of pproceess; welll-orgganizzed; adoppted wideely. The conss: voolumiinouss; ovverkiill ffor mmany typees off proojectts; aagiliity iis quuestiionabble. Althhoughh thee spiirit of tthe CCMMI shouuld aalwayys bee adooptedd, eaach pproceess mmust be aadaptted tto meeet tt

27、he nneedss of the projject teamm andd to achiieve highh quaalityy in the end prodduct. Thee reqquireementts off thee CMMMI shhouldd be appllied to aall pproceess mmodells, bbut ffailuure tto meeet aa speecifiic crriterrion shouuld nnot nnecesssariily mmean thatt thee proocesss is “badd.” IIt maay be

28、e thaat thhe CMMMI iis riight in ssituaationns inn whiich aan orrganiizatiionall cullturee is amenndablle too thee staandarrd prrocesss moodelss andd mannagemment is ccommiittedd to makiing iit a succcess. Howweverr it may be ttoo mmuch for an oorgannizattion to ssucceessfuully assiimilaate. Thiss m

29、eaans tthat CMMII whiich iis riight for one comppany cultture may not be rrightt forr anootherr.2.6) Proccess frammeworrk iss appplicaable to aall tthe pprojeects; hennce tthe ssame frammeworrk acctiviitiess aree apppliedd forr alll proojectts, rregarrdlesss off thee proojectts sizee or compplexiity

30、. A prrocesss frramewwork invoolvess heaavy ccommuunicaationn witth thhe cuustommer tto gaatherr reqquireementts; tthis actiivityy esttabliishess a pplan for the softtwaree enggineeeringg worrk thhat ffolloows. It iinvollves creaationn of modeels tthat willl asssist the deveelopeer annd thhe cuustom

31、mer tto unndersstandd thee reqquireementts annd deesignn theem; iit thherebby innvolvves cconsttructtion (codde geeneraationn andd errror ttestiing). It finaally provvidess feeedbacck baased on tthe eevaluuatioon.2.7) Umbrrellaa acttivitties occuur thhrougghoutt thee sofftwarre prrocesss buut thhey

32、aare nnot nnecesssariily aappliied eevenlly accrosss thee proocesss. Foor exxamplle, ttheree is a heeavy conccentrratioon onn rissk annalyssis ddurinng prrojecct pllanniing, and riskk anaalysiis iss theen reevisiited duriing llaterr fraamewoork aactivvitiees, bbut iit iss nott apppliedd eveenly duri

33、ing tthesee acttivitties. On theootherr hannd, SSQA iis appplieed faairlyy eveenly for all proccess actiivitiies.2.8) The suppport phasse iss apppliedd difffereentlyy forr embbeddeed sooftwaare. In mmost casees, eembeddded softtwaree is defiined and deveelopeed, bbut oonce it iis pllacedd in its hos

34、tt envvironnmentt, itt is not likeely tto chhangee unttil aa neww relleasee of the prodduct occuurs.2.9)Desiggnerss shoould ask userrs: What do yyou wwant thiss prooductt to accoompliish?What key outpputs are prodducedd by the softtwaree?What funcctionns annd feeaturres aare yyou llookiing ffor? Wha

35、t outpputs, funnctioons aand ffeatuures are likeely tto chhangee oveer thhe neext 66 monnths, 1 yyear.Are ttheree anyy queestioons tthat I shhouldd havve assks tthat I diidntt?How wwill you deteerminne iff whaat wee buiilt iis whhat yyou wwanteed?Userss shoould ask as ddesiggnerss: Have I maade mmy

36、neeeds cleaar too youu?Do wee havve thhe toools and peopple wwith skillls rrequiired for the deveelopmment?Are tthe rrequiiremeents propperlyy deffinedd, arre addditiionall reqquireementts neeededd.Are tthe pproduuct ffeatuures and funcctionns acchievvablee in the alloottedd timme?Have you talkked t

37、to otther classses of uuserss?Userss shoould ask themmselvves aaboutt thee sofftwarre prroducct thhat iis too be buillt: Have I assked for moree thaan Ill rreallly neeed?Have I seet deeadliines thatt aree unrrealiisticc?Am I unsuure oof ceertaiin fuunctiions and featturess?Wouldd a pprotootypee be h

38、elppful for certtain funcctionns annd feeaturres?Am I commmitteed too worrk wiith tthe ssoftwware desiignerrs ovver tthe llong haull?Desiggnerss shoould ask themmselvves aaboutt sofftwarre prroducct thhat iis too be buillt annd thhe prrocesss thhat wwill usedd to builld itt:Do I undeerstaand tthe ss

39、copee andd purrposee of the softtwaree?Do I undeerstaand tthe ddesiggn isssuess andd connstraaintss?What toolls arre too be usedd?Do I undeerstaand tthe ttechnnologgy annd buusineess aarea thatt thee sofftwarre iss to addrress?Have we eestabblishhed qqualiity ccriteeria thatt cann be usedd to judgge

40、 ouur woork?2.11)Scriipts defiine sspeciific proccess actiivitiies (i.e., prrojecct laaunchh, deesignn, immplemmentaationn, inntegrratioon annd syystemm tesstingg, poostmoortemm) annd otther moree dettaileed woork ffuncttionss (e.g., deveelopmment plannningg, reequirremennts ddevellopmeent, softtwar

41、ee connfiguuratiion mmanaggemennt, aand uunit testt) thhat aare ppart of tthe tteam proccess. Scrriptss mayybe bbenefficiaal whhen aa teaam neeed gguidaance in pplannning and tracckingg itss worrk, eestabblishhing goalls, aand ddefinning effeectivve taask ssets for techhnicaal acctiviitiess. Foor ex

42、xperiienceed teeams, howweverr, thhe sccriptt mayy preecludde “oon-thhe-flly” aadapttatioon thhat iis offten neceessarry inn agiile eenvirronmeents.2.12) Thhe Peersonnal SSoftwware Proccess (PSPP) emmphassizess perrsonaal meeasurremennt off botth thhe woork pproduuct tthat is pproduuced and the resu

43、ultannt quualitty off thee worrk prroducct. TThe PPSP pproceess mmodell deffiness fivve frramewwork actiivitiies: plannningg, hiigh-llevell dessign, higgh-leevel desiign rrevieew, ddevellopmeent, and posttmorttem. In aaddittion PSP makees thhe prractiitionner rrespoonsibble ffor pprojeect pplannning

44、 (e.gg., eestimmatinng annd sccheduulingg) annd emmpoweers tthe ppracttitiooner to ccontrrol tthe qqualiity oof alll sooftwaare wwork prodductss thaat arre deevelooped.Chaptter 333.1)Any softtwaree proojectt thaat haas siignifficannt fuunctiionallity thatt musst bee delliverred iin a veryy tigght (t

45、oo tighht) ttime framme iss a ccandiidatee forr thee inccremeentall appproacch. TThe iidea is tto deeliveer fuunctiionallity in iincreementts. EExampple: a soophissticaated softtwaree prooductt thaat caan bee relleaseed too thee marrketpplacee witth onnly ppartiial ffuncttionaalityyneww andd impprov

46、eed veersioons tto foolloww! Foor exxamplle, wword-proccessiing ssoftwware deveelopeed ussing the incrremenntal paraadigmm migght ddelivver bbasicc fille maanageementt, edditinng annd doocumeent pproduuctioon fuunctiions in tthe ffirstt inccremeent; moree sopphistticatted eeditiing aand ddocumment p

47、rodductiion ccapabbilitties in tthe sseconnd inncremment; speellinng annd grrammaar chheckiing iin thhe thhird incrremennt, aand aadvannced pagee layyout capaabiliity iin thhe foourthh inccremeent. The proccess floww forr anyy inccremeent mmay iincorrporaate tthe pprotootypiing pparaddigm. Inccremee

48、ntall devveloppmentt is partticullarlyy useeful whenn staaffinng iss unaavaillablee forr a ccompllete impllemenntatiion bby thhe buusineess ddeadlline thatt hass beeen esstabllisheed foor thhe prrojecct.3.2)The wateerfalll moodel is aapproopriaate ffor pprojeects withh thee folllowiing ccharaacterri

49、stiics: (1) the probblem is wwell undeerstoood (requuiremmentss aree welll-deefineed); (2) the deliiveryy datte iss reaalisttic; (3) itss unllikelly thhat mmajorr chaangess in requuiremmentss willl bee reqquestted aas thhe prrojecct prroceeeds. Speccificc exaamplees miight be: (1) a weell uunderrsto

50、ood moodifiicatiion tto ann exiistinng prrograam; (2) aa strraighhtforrwardd impplemeentattion of aa nummericcal ccalcuulatiion oor buusineess rrule, eveen iff its coompleex; (3) aa connstraainedd enhhanceementt to an eexistting proggram.3.3) If tthe pplan is tto haave aa proototyype eevolvve innto

51、aa delliverred aappliicatiion, moree riggorouus deesignn rulles aand SSQA pproceedurees muust bbe appplieed frrom tthe bbeginnningg. Inn addditioon, tthe pprotootypee musst bee dessigneed wiith eextennsibiilityy in mindd andd musst bee impplemeentedd usiing aa proogrammmingg envvironnmentt thaat iss

52、 ameenablle too prooducttion systtem ddevellopmeent. Inittiallly, tthe pprotootypee serrves as aa mecchaniism ffor iidenttifyiing ssoftwware requuiremmentss. Onnce aa worrkingg proototyype iis buuilt, it becoomes the skelletonn (frramewwork) forr exttensiions thatt willl caause it tto evvolvee intto

53、 a prodductiion ssysteem.3.4) RAD assuumes thatt a pprojeect ccan bbe moodulaarizeed inn a mmanneer thhat aallowws maajor funcctionnalitty too be deliivereed wiithinn a 660 90 dday ttime framme. AAlthoough thiss is ofteen thhe caase, therre arre siituattionss in whicch tiimeliines are longger. In aa

54、ddittion, RADD asssumess thaat suufficcientt humman rresouurcess willl bee avaailabble tto deeveloop thhe inncremmentss in paraallell. Thhis mmay nnot bbe thhe caase.3.5) Softtwaree appplicaationns thhat aare rrelattivelly eaasy tto prrotottype almoost aalwayys innvolvve huuman-machhine inteeracttio

55、n and/or hheavyy commputeer grraphiics. Otheer apppliccatioons tthat are someetimees ammenabble tto prrotottypinng arre ceertaiin cllassees off matthemaaticaal allgoriithmss, suubsett of commmand drivven ssysteems aand ootherr appplicaationns whhere resuults can be eeasilly exxaminned wwithoout rrea

56、l-timee intteracctionn. Apppliccatioons tthat are moree diffficuult tto prrotottype incllude conttrol and proccess conttrol funcctionns, mmany classses of rreal-timee appplicaationns annd emmbeddded ssoftwware.3.6)The reall queestioon thhat aa papper sshoulld adddresss iss: Hoow doo we deveelop a pr

57、rocesss thhat ccan aaccommmodaate mmany of tthe cchaottic aattriibutees off moddern softtwaree devveloppmentt? Thhe auuthorrs suuggesst prrocessses thatt aree “foocuseed onn fleexibiilityy andd exttensiibiliity rratheer thhan oon hiigh qqualiity” and admiit thhat tthis apprroachh is “scaary.” No dou

58、bbt! IIn faact, I beelievve itt is a reecipee forr dissasteer. WWith the exceeptioon off cerrtainn widdely usedd PC operratinng syystemms (tthat willl remmain nameelesss) quualitty dooes aappeaar too be a reeasonnablee harrbingger oof suuccesssfull sofftwarre. AA proogramm thaat iss “fllexibble aand

59、 eextennsiblle” wwill not succceed if iit faails reguularlly annd beehavees unnpreddictaably. It shouuld bbe nooted thatt mucch haas beeen wwrittten aaboutt “goood eenouggh” ssoftwware. Thaats OK aas loong aas thhe woord “goodd” iss empphasiized.3.7) Proccess modeels ccan bbe coombinned. Eachh modde

60、l ssuggeests a soomewhhat ddiffeerentt proocesss floow, bbut aall pperfoorm tthe ssame set of ggenerric fframeeworkk acttivitties: commmuniicatiion, plannningg, moodeliing, consstrucctionn, annd deeployymentt. Forr exaamplee thee linnear sequuentiial mmodell cann serrve aas a usefful pproceess mmode