軟件工程課后習(xí)題答案

1、PAGE PAGE 70軟件工程課后習(xí)題答案Chapter1The definition for software presented in Section 1.2 applies to the Web sites. There are, however, subtle differences between a Web site and conventional software. Among the most important are that the content that a Web site presents is considered to be part of the Web

2、 Application while that data processed by conventional software is often considered to be separate from the processing functions delivered.Who wouuld haave thhoughtt thatt softtware wouldd leadd to: (1) aa channge inn the datinng habbits oof manny youung peeople (Inteernet datinng); (2) thhe wayy pe

3、opple coommuniicate (celll phonnes); (3) mmethodds of warfaare (ccyberwweaponns); (4) thhe diaagnosiis of diseaases (MRIs and rrelateed commputerr-baseed diaagnosttic deevicess), annd (5) the manneer in whichh peopple accquiree and enjoyy mediia (muusic, DVDs, etc.).The Laww of CConserrvatioon of Fa

4、milliaritty: Ass the systeem evoolves the uusers enginneers, deveeloperrs alll thosse asssociatted muust haave thhe commpletee knowwledgee of tthe coontentt and behavvior tto achhieve satissfactoory reesultss. Inccreasee in ggrowthh may diminnish tthat kknowleedge (masteery); hencee the averaage inn

5、creasse in growtth remmains invarriant as thhe sysstem eevolvees.Many moodern appliicatioons chhange frequuentlyy befoore thhey arre preesenteed to the eend usser annd theen aftter thhe firrst veersionns havve beeen useed. A few wways tto buiild sooftwarre to stop deterriorattion ddue too channge wo

6、ould bbe: Make suure thhat sooftwarre is desiggned sso thaat chaanges in onne parrt of a proogram do noot creeate sside-eeffectts in anothher paart off the progrram.Make suure thhat sooftwarre is desiggned sso thaat it does not ddependd on eexternnal deevicess or ssystemms thaat aree likeely too cha

7、nnge wiith tiime.Make suure teest caases aand reesultss are archiived aand avvailabble soo thatt the softwware ccan bee reteested when changges arre madde.Make suure yoou speend tiime unndersttandinng whaat thee custtomer wantss.The twoo broaadest categgoriess encoompasss riskks asssociatted wiith e

8、cconomiic losss andd riskks to the wwell bbeing of peeople. It mmight be a good idea to seelect five riskss (cullled ffrom tthe soourcess noteed) annd preesent them to thhe claass. LLook ffor huumorouus as well as seeriouss riskks.The samme appproachh to ssoftwaare enngineeering can bbe appplied for

9、 eeach oof thee six categgoriess, butt it mmust bbe adaapted to acccommoodate the sspeciaal reqquiremments of eaach caategorry. There aare liiterallly doozens of reeal liife ciircumsstancees to choosse froom. Foor exaample, softtware errorrs thaat havve cauused mmajor telepphone netwoorks tto faiil,

10、 faailurees in avionnics tthat hhave ccontriibutedd to pplane crashhes, ccomputter viirusess (e.gg., Miichelaangeloo) thaat havve cauused ssignifficantt econnomic lossees andd attaacks oon majjor e-commeerce ssites.The Laww of DDeclinning QQualitty: Thhe quaality of syystemss willl declline uunlesss

11、 theyy are mainttainedd by vvariouus proocedurres too adappt to the eenviroonmenttal chhangess. Thiis conncept is siimilarr to tthe “ddeteriioratiion” ddiscusssed iin Prooblem 1-5.The Laww of CConserrvatioon of Organnizatiional Stabiility: The averaage efffectiive gllobal activvity rrate iis invvari

12、annt oveer thee lifeetime of a produuct.Chapterr 22.1)Patternn: CommuunicattionIntent:To esstabliish a collaaborattive rrelatiionshiip witth thee custtomer in ann effoort too defiine prrojectt scoppe, buusinesss reqquiremments and oother projeect coonstraaints.” Type: Stagee pattternInitiall conttex

13、t: (1) AApproppriatee stakkeholdders hhave bbeen iidentiified and aare wiillingg to pparticcipatee in ccommunnicatiion (22) Staakehollders agreee thatt a prroblemm exissts annd thaat sofftwaree may proviide a soluttion Problemm: Requiiremennts muust bee eliccited from stakeeholdeers annd orgganizeed

14、 in a wayy thatt can be ussed byy softtware enginneers. All stakeeholdeers muust coollaboorate to deefine requiiremennts annd to identtify tthose areass wherre reqquiremments are uuncerttain.Solutioon:Each stakeeholdeer musst devvelop a desscripttion oof thee funcctionss, feaaturess, infformattion a

15、and beehavioor thaat aree exhiibitedd by tthe sooftwarre. Too accoomplissh thiis, a struccturedd, faccilitaated meetiing iss condductedd. Forr moree detaails, see SSectioons 7.3, 7.4 andd 7.5.Resultiing Coontextt:When this patteern haas beeen succcessffully complleted, basiic infformattion rrequirre

16、d foor thee deveelopmeent off an aanalyssis moodel hhas beeen accquireed andd docuumenteed in some manneer. Usse-casses (uuser sscenarrios) have been develloped, alonng witth bassic deescripptionss of ssystemm funcction and bbehaviior annd thee dataa objeects tthat aare too be mmanipuulatedd and/or

17、prroduceed/Relatedd Pattterns: Condductedd a meeetingg; reqquiremment ggatherring; devellopingg use-casess; buiildingg a miini-sppec; nnegotiiatingg requuiremeents, priorritizaation. Known Uses/Exampples: Commuunicattion iis manndatorry at the bbeginnning oof eveery sooftwarre prooject; is rrecommme

18、ndedd throoughouut thee softtware projeect; aand iss manddatoryy oncee the deplooymentt actiivity is unnderwaay.2.2) Proceess asssessmment eexaminnes thhe sofftwaree proccess uused bby an organnizatiion too deteerminee whetther iit is effecctive in acchieviing sooftwarre enggineerring ggoals. Thee a

19、sseessmennt chaaracteerizess the curreent prracticce witthin aan orgganizaationaal uniit in termss of tthe caapabillity oof thee seleected proceesses. The SPICEE (ISOO/IEC115504) stanndard definnes a set oof reqquiremments for ssoftwaare prrocesss asseessmennt. Too accoomplissh thee asseessmennt, SP

20、PICE sspeciffies aa “refferencce moddel” tthat eexaminnes thhe purrpose and mmeasurrable objecctivess of tthe prrocesss (thee “proocess dimennsion”) and the sset off proccess aattribbutes that shoulld be preseent (tthe “ccapabiility dimennsion”).2.4) Taskk Set for CCommunnicatiion Acctivitty: A task

21、 set wwould definne thee actuual woork too be ddone tto acccompliish thhe objjectivves off a sooftwarre enggineerring aactionn. Forr the commuunicattion aactiviity thhese aare: Make a list of sttakehoolderss for the pprojecctInvite all tthe sttakehoolderss to aan infformall meettingAsk theem to make

22、 a lisst of featuures aand fuunctioonsDiscusss requuiremeents aand buuild aa finaal lisstPriorittize rrequirrementts andd notee the areass thatt stakkeholdders aare unncertaain offThese ttasks may bbe exppandedd for a commplex softwware pprojecct, thhey maay theen connsiderr the folloowing: To condd

23、uct aa seriies off speccificaation meetiings, buildd a prrelimiinary list of fuunctioons annd feaaturess baseed on stakeeholdeer inpput.To builld a rreviseed lisst of stakee holdder reequireementss use qualiity fuunctioon depploymeent teechniqques tto priiotizee the requiiremennts.Note coonstraaints

24、 and rrestriictionns on the ssystemm.Discusss methhods ffor vaalidatting ssystemm.2.5)Thhe CMMMI reppresennts a proceess meetamoddel inn 2 diiffereent waaysthhe conntinuoous annd thee stagged moodel. The ppros oof thee CMMII: commpreheensivee, adddressiing viirtuallly evvery aaspectt of pprocesss; w

25、eell-orrganizzed; aadopteed widdely. The ccons: volumminouss; oveerkilll for many typess of pprojeccts; aagilitty is questtionabble. AAlthouugh thhe spiirit oof thee CMMII shouuld allways be addoptedd, eacch proocess must be addaptedd to mmeet tthe neeeds oof thee projject tteam aand too achiieve hh

26、igh qqualitty in the eend prroductt. Thee requuiremeents oof thee CMMII shouuld bee appllied tto alll proccess mmodelss, butt faillure tto meeet a sspeciffic crriteriion shhould not nnecesssarilyy meann thatt the proceess iss “badd.” Itt may be thhat thhe CMMMI is rightt in ssituattions in whhich aa

27、n orgganizaationaal cullture is ammendabble too the standdard pprocesss moddels aand maanagemment iis commmitteed to makinng it a succcess. Howeever iit mayy be ttoo muuch foor an organnizatiion too succcessfuully aassimiilate. Thiss meanns thaat CMMMI whiich iss righht forr one compaany cuulturee m

28、ay not bbe rigght foor anoother.2.6) Proceess frramewoork iss appllicablle to all tthe prrojectts; heence tthe saame frramewoork acctivitties aare apppliedd for all pprojeccts, rregarddless of thhe proojects siize orr compplexitty. A proceess frramewoork innvolvees heaavy coommuniicatioon witth thee

29、 custtomer to gaather requiiremennts; tthis aactiviity esstabliishes a plaan forr the softwware eengineeeringg workk thatt folllows. It innvolvees creeationn of mmodelss thatt willl assiist thhe devvelopeer andd the custoomer tto undderstaand thhe reqquiremments and ddesignn themm; it thereeby innvo

30、lvees connstrucction (codee geneeratioon andd erroor tessting). It finallly prrovidees feeedbackk baseed on the eevaluaation.2.7) Umbreella aactiviities occurr throoughouut thee softtware proceess buut theey aree not necesssarilly appplied evenlly acrross tthe prrocesss. Forr exammple, theree is aa

31、heavvy conncentrrationn on rrisk aanalyssis duuring projeect pllanninng, annd rissk anaalysiss is tthen rrevisiited dduringg lateer fraameworrk acttivitiies, bbut itt is nnot apppliedd evennly duuring thesee actiivitiees. Onn theoother hand, SQA is apppliedd fairrly evvenly for aall prrocesss actiiv

32、itiees.2.8) TThe suupportt phasse is appliied diiffereently for eembeddded sooftwarre. Inn mostt casees, emmbeddeed sofftwaree is ddefineed andd deveelopedd, butt oncee it iis plaaced iin itss hostt enviironmeent, iit is not llikelyy to cchangee untiil a nnew reeleasee of tthe prroductt occuurs.2.9)

33、Designeers shhould ask uusers: What doo you want this produuct too accoomplissh?What keey outtputs are pproducced byy the softwware?What fuunctioons annd feaaturess are you llookinng forr? What ouutputss, funnctionns andd feattures are llikelyy to cchangee overr the next 6 monnths, 1 yeaar.Are theer

34、e anny queestionns thaat I sshouldd havee askss thatt I diidnt?How willl youu deteerminee if wwhat wwe buiilt iss whatt you wanteed?Users sshouldd ask as deesigneers: Have I made my neeeds cclear to yoou?Do we hhave tthe toools aand peeople with skillls reqquiredd for the ddeveloopmentt?Are thee req

35、uuiremeents pproperrly deefinedd, aree addiitionaal reqquiremments needeed.Are thee prodduct ffeaturres annd funnctionns achhievabble inn the allottted ttime?Have yoou tallked tto othher cllassess of uusers?Users sshouldd ask themsselvess abouut thee softtware produuct thhat iss to bbe buiilt: Have

36、I askedd for more than Ill reallly neeed?Have I set ddeadliines tthat aare unnrealiistic?Am I unnsure of ceertainn funcctionss and featuures?Would aa prottotypee be hhelpfuul forr certtain ffunctiions aand feeaturees?Am I coommittted too workk withh the softwware ddesignners oover tthe loong haaul?D

37、esigneers shhould ask tthemseelves aboutt softtware produuct thhat iss to bbe buiilt annd thee proccess tthat wwill uused tto buiild itt:Do I unndersttand tthe sccope aand puurposee of tthe sooftwarre?Do I unndersttand tthe deesign issuees andd consstrainnts?What toools aare too be uused?Do I unnder

38、sttand tthe teechnollogy aand buusinesss areea thaat thee softtware is too addrress?Have wee estaablishhed quualityy critteria that can bbe useed to judgee our work?2.11)SScriptts deffine sspeciffic prrocesss actiivitiees (i.e., pprojecct lauunch, desiggn, immplemeentatiion, iintegrrationn and syste

39、em tessting, posttmorteem) annd othher moore deetaileed worrk funnctionns (e.g., ddeveloopmentt plannning, requuiremeents ddeveloopmentt, sofftwaree conffiguraation managgementt, andd unitt testt) thaat aree partt of tthe teeam prrocesss. Scrripts maybee beneeficiaal wheen a tteam nneed gguidannce i

40、nn plannning and ttrackiing itts worrk, esstabliishingg goalls, annd deffiningg effeectivee taskk setss for technnical activvitiess. Forr expeeriencced teeams, howevver, tthe sccript may pprecluude “oon-thee-fly” adapttationn thatt is ooften necesssary in aggile eenviroonmentts.2.12) The PPersonnal

41、Sooftwarre Proocess (PSP) emphhasizees perrsonall meassuremeent off bothh the work produuct thhat iss prodduced and tthe reesultaant quualityy of tthe woork prroductt. Thee PSP proceess moodel ddefinees fivve fraameworrk acttivitiies: pplanniing, hhigh-llevel desiggn, hiigh-leevel ddesignn reviiew,

42、ddeveloopmentt, andd posttmorteem. Inn addiition PSP mmakes the ppractiitioneer ressponsiible ffor prrojectt plannning (e.g., esttimatiing annd schheduliing) aand emmpowerrs thee pracctitiooner tto conntrol the qqualitty of all ssoftwaare woork prroductts thaat aree deveelopedd.Chapterr 33.1)Anny so

43、fftwaree projject tthat hhas siignifiicant functtionallity tthat mmust bbe dellivereed in a verry tigght (ttoo tiight) time framee is aa canddidatee for the iincremmentall apprroach. The idea is too deliiver ffunctiionaliity inn incrrementts. Exxamplee: a ssophissticatted sooftwarre prooduct that ca

44、n bbe relleasedd to tthe maarketpplace with only partiial fuunctioonalittyneww and improoved vversioons too folllow! FFor exxamplee, worrd-proocessiing sooftwarre devvelopeed usiing thhe inccremenntal pparadiigm miight ddeliveer bassic fiile maanagemment, editiing annd doccumentt prodductioon funnct

45、ionns in the ffirst increement; moree sophhisticcated editiing annd doccumentt prodductioon cappabiliities in thhe seccond iincremment; spellling aand grrammarr checcking in thhe thiird inncremeent, aand addvanceed pagge layyout ccapabiility in thhe fouurth iincremment. The pprocesss floow forr any

46、increement may iincorpporatee the protootypinng parradigmm. Inccremenntal ddeveloopmentt is pparticcularlly useeful wwhen sstaffiing iss unavvailabble foor a ccompleete immplemeentatiion byy the businness ddeadliine thhat haas beeen esttablisshed ffor thhe prooject.3.2)Thhe watterfalll moddel iss ap

47、prropriaate foor proojectss withh the folloowing charaacteriisticss: (1) the probllem iss welll undeerstoood (reequireementss are well-definned); (2) tthe deeliverry datte is realiistic; (3) its unlikkely tthat mmajor changges inn requuiremeents wwill bbe reqquesteed as the pprojecct prooceedss. Spe

48、ecificc exammples mightt be: (1) aa welll undeerstoood moddificaation to ann exissting progrram; (2) a straiightfoorwardd impllementtationn of aa numeericall calcculatiion orr busiiness rule, evenn if iits ccompleex; (33) a cconstrrainedd enhaancemeent too an eexistiing prrogramm.3.3) If thhe plaan

49、is to haave a protootype evolvve intto a ddeliveered aappliccationn, morre riggorouss desiign ruules aand SQQA proocedurres muust bee appllied ffrom tthe beeginniing. IIn addditionn, thee prottotypee mustt be ddesignned wiith exxtensiibilitty in mind and mmust bbe impplemennted uusing a proogrammmin

50、g eenviroonmentt thatt is aamenabble too prodductioon sysstem ddeveloopmentt. Iniitiallly, thhe proototyppe serrves aas a mmechannism ffor iddentiffying softwware rrequirrementts. Onnce a workiing prrototyype iss buillt, itt becoomes tthe skkeletoon (frramewoork) ffor exxtensiions tthat wwill ccause

51、 it too evollve innto a produuctionn systtem.3.4) RAD aassumees thaat a pprojecct cann be mmodulaarizedd in aa mannner thhat alllows majorr funcctionaality to bee deliiveredd withhin a 60 90 daay timme fraame. AAlthouugh thhis iss ofteen thee casee, theere arre sittuatioons inn whicch timmelinees ar

52、ee longger. IIn addditionn, RADD assuumes tthat ssufficcient humann resoourcess willl be aavailaable tto devvelop the iincremments in paaralleel. Thhis maay nott be tthe caase.3.5) SSoftwaare appplicaationss thatt are relattivelyy easyy to pprotottype aalmostt alwaays innvolvee humaan-macchine inter

53、ractioon andd/or hheavy compuuter ggraphiics. OOther appliicatioons thhat arre sommetimees ameenablee to pprotottypingg are certaain cllassess of mmathemmaticaal alggorithhms, ssubsett of ccommannd driiven ssystemms andd otheer appplicattions wheree resuults ccan bee easiily exxamineed witthout real

54、-time interractioon. Appplicaationss thatt are more diffiicult to prrototyype inncludee conttrol aand prrocesss conttrol ffunctiions, many classses off reall-timee appllicatiions aand emmbeddeed sofftwaree.3.6)Thhe reaal queestionn thatt a paaper sshouldd addrress iis: Hoow do we deevelopp a prroces

55、ss thatt can accommmodatte manny of the cchaotiic atttributtes off modeern sooftwarre devvelopmment? The aauthorrs sugggest proceesses that are “ffocuseed on flexiibilitty andd exteensibiility ratheer thaan on high qualiity” aand addmit tthat tthis aapproaach iss “scaary.” No dooubt! In faact, II be

56、liieve iit is a reccipe ffor diisasteer. Wiith thhe excceptioon of certaain wiidely used PC opperatiing syystemss (thaat willl remmain nnameleess) qqualitty doees apppear tto be a reaasonabble haarbingger off succcessfuul sofftwaree. A pprograam thaat is “flexxible and eextenssible” will not ssuccee

57、ed if it faails rregulaarly aand beehavess unprredicttably. It sshouldd be nnoted that much has bbeen wwritteen aboout “ggood eenoughh” sofftwaree. Thaats OOK as long as thhe worrd “goood” iis empphasizzed.3.7) Proceess moodels can bbe commbinedd. Eacch moddel suuggestts a ssomewhhat diiffereent prr

58、ocesss floww, butt all perfoorm thhe samme sett of ggeneriic fraameworrk acttivitiies: ccommunnicatiion, pplanniing, mmodeliing, cconstrructioon, annd depploymeent. For eexamplle thee lineear seequenttial mmodel can sserve as a usefuul proocess modell in ssituattions wheree requuiremeents aare fiixe

59、d aand woork iss to pproceeed to complletionn in aa lineear maanner. In ccases, wherre thee deveeloperr may be unnsure of thhe effficienncy off an aalgoriithm, the aadaptaabilitty of an opperatiing syystem, or tthe foorm thhat huuman-mmachinne intteracttion sshouldd takee. In thesee, andd manyy othe

60、er sittuatioons, aa prottotypiing moodel mmay offfer tthe beest appproacch. Inn otheer casses, aan inccremenntal aapproaach maay makke sennse annd thee floww of SSpirall modeel mayy be eefficiient. Speciial prrocesss modeels taake onn manyy of tthe chharactteristtics oof onee or mmore oof thee tradd