軟件工程-敏捷開發(fā)(中英文對照)教學文稿

軟件工程-敏捷開發(fā)(中英文對照)極限編程

（ExtremeProgramming，簡稱為XP）敏捷開發(fā)被認為是一種“輕量級”的方法。在輕量級方法中最負盛名的應該是“極限編程”（ExtremeProgramming，簡稱為XP）。而與輕量級方法相對應的是“重量級方法”的存在。重量級方法強調(diào)以開發(fā)過程為中心，而不是以人為中心。ExtremeProgramming(XP)isasoftwaredevelopmentmethodologywhichisintendedtoimprovesoftwarequalityandresponsivenesstochangingcustomerrequirements.Asatypeofagilesoftwaredevelopment,itadvocatesfrequent"releases"inshortdevelopmentcycles(timeboxing),whichisintendedtoimproveproductivityandintroducecheckpointswherenewcustomerrequirementscanbeadopted.OtherelementsofExtremeProgramminginclude:programminginpairsordoingextensivecodereview,unittestingofallcode,avoidingprogrammingoffeaturesuntiltheyareactuallyneeded,aflatmanagementstructure,simplicityandclarityincode,expectingchangesinthecustomer'srequirementsastimepassesandtheproblemisbetterunderstood,andfrequentcommunicationwiththecustomerandamongprogrammers.Themethodologytakesitsnamefromtheideathatthebeneficialelementsoftraditionalsoftwareengineeringpracticesaretakento"extreme"levels,onthetheorythatifalittleisgood,moreisbetter.Criticshavenotedseveralpotentialdrawbacks弊端,

includingproblemswithunstablerequirements,nodocumentedcompromises(妥協(xié)、折衷)

ofuserconflicts(爭執(zhí)),andalackofanoveralldesignspecificationordocument.重量級方法呈現(xiàn)的是一種“防御型”的姿態(tài)。在應用“重量級方法”的軟件組織中，由于軟件項目經(jīng)理不參與或者很少參與程序設計，無法從細節(jié)上把握項目進度，因而會對項目產(chǎn)生“恐懼感”，不得不要求程序員不斷撰寫很多“軟件開發(fā)文檔”。輕量級方法則呈現(xiàn)“進攻型”的姿態(tài)，這一點從XP方法特別強調(diào)的五種價值溝通communication，簡單simplicity，反饋feedback，勇氣courage，尊重respect。

ThevaluesofXP:

1.CommunicationBuildingsoftwaresystemsrequirescommunicatingsystemrequirementstothedevelopersofthesystem.Informalsoftwaredevelopmentmethodologies,thistaskisaccomplishedthroughdocumentation.Extremeprogrammingtechniquescanbeviewedasmethodsforrapidlybuildinganddisseminating散播institutionalknowledgeamongmembersofadevelopmentteam.Thegoalistogivealldevelopersasharedviewofthesystemwhichmatchestheviewheldbytheusersofthesystem.Tothisend,extremeprogrammingfavorssimpledesigns,commonmetaphors,collaborationofusersandprogrammers,frequentverbalcommunication,andfeedback.

ThevaluesofXP:2.SimplicityExtremeprogrammingencouragesstartingwiththesimplestsolution.Extrafunctionalitycanthenbeaddedlater.Thedifferencebetweenthisapproachandmoreconventionalsystemdevelopmentmethodsisthefocusondesigningandcodingfortheneedsoftodayinsteadofthoseoftomorrow,nextweek,ornextmonth.Thisissometimessummedupasthe"youain'tgonnaneedit"(YAGNI)approach.適可而止的設計"Youain'tgonnaneedit"or“Youaren′tgonnaneedit”(acronym:YAGNI)istheprincipleinextremeprogrammingthatprogrammersshouldnotaddfunctionalityuntilitisnecessary.RonJeffrieswrites,"Alwaysimplementthingswhenyouactuallyneedthem,neverwhenyoujustforeseethatyouneedthem."

ThevaluesofXP:2.SimplicityProponents支持者ofXPacknowledgethedisadvantagethatthiscansometimesentailmoreefforttomorrowtochangethesystem;theirclaimisthatthisismorethancompensatedforbytheadvantageofnotinvestinginpossiblefuturerequirementsthatmightchangebeforetheybecomerelevant.Codinganddesigningforuncertainfuturerequirementsimpliestheriskofspendingresourcesonsomethingthatmightnotbeneeded.Relatedtothe"communication"value,simplicityindesignandcodingshouldimprovethequalityofcommunication.Asimpledesignwithverysimplecodecouldbeeasilyunderstoodbymostprogrammersintheteam.

ThevaluesofXP:3.FeedbackWithinextremeprogramming,feedbackrelatestodifferentdimensionsofthesystemdevelopment:Feedbackfromthesystem:bywritingunittests,orrunningperiodicintegrationtests,theprogrammershavedirectfeedbackfromthestateofthesystemafterimplementingchanges.Feedbackfromthecustomer:Thefunctionaltests(aka又叫做；亦稱為(=alsoknownas)

acceptancetests)arewrittenbythecustomerandthetesters.Theywillgetconcretefeedbackaboutthecurrentstateoftheirsystem.Thisreviewisplannedonceineverytwoorthreeweekssothecustomercaneasilysteerthedevelopment.Feedbackfromtheteam:Whencustomerscomeupwithnewrequirementsintheplanninggametheteamdirectlygivesanestimationofthetimethatitwilltaketoimplement.

ThevaluesofXP:3.FeedbackFeedbackiscloselyrelatedtocommunicationandsimplicity.Flawsinthesystemareeasilycommunicatedbywritingaunittestthatprovesacertainpieceofcodewillbreak.Thedirectfeedbackfromthesystemtellsprogrammerstorecodethispart.Acustomerisabletotestthesystemperiodicallyaccordingtothefunctionalrequirements,knownasuserstories.ToquoteKentBeck,"Optimismisanoccupationalhazardofprogramming.Feedbackisthetreatment."

ThevaluesofXP:4.CourageSeveralpracticesembodycourage.Oneisthecommandmenttoalwaysdesignandcodefortodayandnotfortomorrow.Thisisanefforttoavoidgettingboggeddownindesignandrequiringalotofefforttoimplementanythingelse.Courageenablesdeveloperstofeelcomfortablewithrefactoringtheircodewhennecessary.Thismeansreviewingtheexistingsystemandmodifyingitsothatfuturechangescanbeimplementedmoreeasily.Anotherexampleofcourageisknowingwhentothrowcodeaway:couragetoremovesourcecodethatisobsolete,nomatterhowmucheffortwasusedtocreatethatsourcecode.

ThevaluesofXP:4.CourageAlso,couragemeanspersistence:Aprogrammermightbestuckonacomplexproblemforanentireday,thensolvetheproblemquicklythenextday,ifonlytheyarepersistent.

ThevaluesofXP:5.Respect

Therespectvalueincludesrespectforothersaswellasself-respect.Programmersshouldnevercommitchangesthatbrea