软件工程-敏捷开发(中英文对照)教学文稿

软件工程-敏捷开发(中英文对照)极限编程

（ExtremeProgramming，简称为XP）敏捷开发被认为是一种“轻量级”的方法。在轻量级方法中最负盛名的应该是“极限编程”（ExtremeProgramming，简称为XP）。而与轻量级方法相对应的是“重量级方法”的存在。重量级方法强调以开发过程为中心，而不是以人为中心。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(妥协、折衷)

ofuserconflicts(争执),andalackofanoveralldesignspecificationordocument.重量级方法呈现的是一种“防御型”的姿态。在应用“重量级方法”的软件组织中，由于软件项目经理不参与或者很少参与程序设计，无法从细节上把握项目进度，因而会对项目产生“恐惧感”，不得不要求程序员不断撰写很多“软件开发文档”。轻量级方法则呈现“进攻型”的姿态，这一点从XP方法特别强调的五种价值沟通communication，简单simplicity，反馈feedback，勇气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.适可而止的设计"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；亦称为(=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