xp极限模型 Extreme programmingWord文档下载推荐.docx

xp极限模型 Extreme programmingWord文档下载推荐.docx

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Criticshavenotedseveralpotentialdrawbacks,[5]includingproblemswithunstablerequirements,nodocumentedcompromisesofuserconflicts,andalackofanoveralldesignspecificationordocument.

Contents

聽[hide]聽

∙1History

o1.1Origins

o1.2Currentstate

∙2Concept

o2.1Goals

o2.2Activities

▪2.2.1Coding

▪2.2.2Testing

▪2.2.3Listening

▪2.2.4Designing

o2.3Values

▪2.3.1Communication

▪2.3.2Simplicity

▪2.3.3Feedback

▪2.3.4Courage

▪2.3.5Respect

o2.4Rules

o2.5Principles

▪2.5.1Feedback

▪2.5.2Assumingsimplicity

▪2.5.3Embracingchange

∙3Practices

o3.1Fine-scalefeedback

o3.2Continuousprocess

o3.3Sharedunderstanding

o3.4Programmerwelfare

o3.5Coding

o3.6Testing

∙4Controversialaspects

o4.1Scalability

o4.2Severabilityandresponses

∙5Criticism

∙6Seealso

∙7References

∙8Furtherreading

∙9Externallinks

History[edit]

ExtremeProgrammingwascreatedbyKentBeckduringhisworkontheChryslerComprehensiveCompensationSystem（C3）payrollproject.[5]BeckbecametheC3projectleaderinMarch1996andbegantorefinethedevelopmentmethodologyusedintheprojectandwroteabookonthemethodology（inOctober1999,ExtremeProgrammingExplainedwaspublished）.[5]ChryslercancelledtheC3projectinFebruary2000,aftersevenyears,whenthecompanywasacquiredbyDaimler-Benz.[6]

Althoughextremeprogrammingitselfisrelativelynew,manyofitspracticeshavebeenaroundforsometime;

themethodology,afterall,takes"

bestpractices"

toextremelevels.Forexample,the"

practiceoftest-firstdevelopment,planningandwritingtestsbeforeeachmicro-increment"

wasusedasearlyasNASA'

sProjectMercury,intheearly1960s（Larman2003）.Toshortenthetotaldevelopmenttime,someformaltestdocuments（suchasforacceptancetesting）havebeendevelopedinparallel（orshortlybefore）thesoftwareisreadyfortesting.ANASAindependenttestgroupcanwritethetestprocedures,basedonformalrequirementsandlogicallimits,beforethesoftwarehasbeenwrittenandintegratedwiththehardware.InXP,thisconceptistakentotheextremelevelbywritingautomatedtests（perhapsinsideofsoftwaremodules）whichvalidatetheoperationofevensmallsectionsofsoftwarecoding,ratherthanonlytestingthelargerfeatures.

Origins[edit]

Softwaredevelopmentinthe1990swasshapedbytwomajorinfluences:

internally,object-orientedprogrammingreplacedproceduralprogrammingastheprogrammingparadigmfavoredbysomeintheindustry;

externally,theriseoftheInternetandthedot-comboomemphasizedspeed-to-marketandcompanygrowthascompetitivebusinessfactors.Rapidlychangingrequirementsdemandedshorterproductlife-cycles,andwereoftenincompatiblewithtraditionalmethodsofsoftwaredevelopment.

TheChryslerComprehensiveCompensationSystem（C3）wasstartedinordertodeterminethebestwaytouseobjecttechnologies,usingthepayrollsystemsatChryslerastheobjectofresearch,withSmalltalkasthelanguageandGemStoneasthedataaccesslayer.TheybroughtinKentBeck,[5]aprominentSmalltalkpractitioner,todoperformancetuningonthesystem,buthisroleexpandedashenotedseveralproblemstheywerehavingwiththeirdevelopmentprocess.Hetookthisopportunitytoproposeandimplementsomechangesintheirpracticesbasedonhisworkwithhisfrequentcollaborator,WardCunningham.Beckdescribestheearlyconceptionofthemethods:

[7]

ThefirsttimeIwasaskedtoleadateam,IaskedthemtodoalittlebitofthethingsIthoughtweresensible,liketestingandreviews.Thesecondtimetherewasalotmoreontheline.Ithought,"

Damnthetorpedoes,atleastthiswillmakeagoodarticle,"

[and]askedtheteamtocrankupalltheknobsto10onthethingsIthoughtwereessentialandleaveouteverythingelse.

BeckinvitedRonJeffriestotheprojecttohelpdevelopandrefinethesemethods.JeffriesthereafteractedasacoachtoinstillthepracticesashabitsintheC3team.

InformationabouttheprinciplesandpracticesbehindXPwasdisseminatedtothewiderworldthroughdiscussionsontheoriginalwiki,Cunningham'

sWikiWikiWeb.Variouscontributorsdiscussedandexpandedupontheideas,andsomespin-offmethodologiesresulted（seeagilesoftwaredevelopment）.Also,XPconceptshavebeenexplained,forseveralyears,usingahypertextsystemmapontheXPwebsiteat"

http:

//www.extremeprogramming.org"

circa1999.

BeckeditedaseriesofbooksonXP,beginningwithhisownExtremeProgrammingExplained（1999,ISBN0-201-61641-6）,spreadinghisideastoamuchlargeraudience.AuthorsintheserieswentthroughvariousaspectsattendingXPanditspractices.Theseriesincludedabookthatwascriticalofthepractices.

Currentstate[edit]

XPgeneratedsignificantinterestamongsoftwarecommunitiesinthelate1990sandearly2000s,seeingadoptioninanumberofenvironmentsradicallydifferentfromitsorigins.

Thehighdisciplinerequiredbytheoriginalpracticesoftenwentbythewayside,causingsomeofthesepractices,suchasthosethoughttoorigid,tobedeprecatedorreduced,orevenleftunfinished,onindividualsites.Forexample,thepracticeofend-of-dayintegrationtestsforaparticularprojectcouldbechangedtoanend-of-weekschedule,orsimplyreducedtomutuallyagreeddates.Suchamorerelaxedschedulecouldavoidpeoplefeelingrushedtogenerateartificialstubsjusttopasstheend-of-daytesting.Aless-rigidscheduleallows,instead,forsomecomplexfeaturestobemorefullydevelopedoveraseveral-dayperiod.However,somelevelofperiodicintegrationtestingcandetectgroupsofpeopleworkinginnon-compatible,tangenteffortsbeforetoomuchworkisinvestedindivergent,wrongdirections.

Meanwhile,otheragiledevelopmentpracticeshavenotstoodstill,andXPisstillevolving,assimilatingmorelessonsfromexperiencesinthefield,touseotherpractices.InthesecondeditionofExtremeProgrammingExplained（November2004）,fiveyearsafterthefirstedition,Beckaddedmorevaluesandpracticesanddifferentiatedbetweenprimaryandcorollarypractices.

Concept[edit]

Goals[edit]

ExtremeProgrammingExplaineddescribesextremeprogrammingasasoftware-developmentdisciplinethatorganizespeopletoproducehigher-qualitysoftwaremoreproductively.

XPattemptstoreducethecostofchangesinrequirementsbyhavingmultipleshortdevelopmentcycles,ratherthanalongone.Inthisdoctrine,changesareanatural,inescapableanddesirableaspectofsoftware-developmentprojects,andshouldbeplannedfor,insteadofattemptingtodefineastablesetofrequirements.

Extremeprogrammingalsointroducesanumberofbasicvalues,principlesandpracticesontopoftheagileprogrammingframework.

Activities[edit]

XPdescribesfourbasicactivitiesthatareperformedwithinthesoftwaredevelopmentprocess:

coding,testing,listening,anddesigning.Eachofthoseactivitiesisdescribedbelow.

Coding[edit]

TheadvocatesofXParguethattheonlytrulyimportantproductofthesystemdevelopmentprocessiscode鈥?

softwareinstructionsthatacomputercaninterpret.Withoutcode,thereisnoworkingproduct.

Codingcanalsobeusedtofigureoutthemostsuitablesolution.Codingcanalsohelptocommunicatethoughtsaboutprogrammingproblems.Aprogrammerdealingwithacomplexprogrammingproblem,orfindingithardtoexplainthesolutiontofellowprogrammers,mightcodeitinasimplifiedmannerandusethecodetodemonstratewhatheorshemeans.Code,saytheproponentsofthisposition,isalwaysclearandconciseandcannotbeinterpretedinmorethanoneway.Otherprogrammerscangivefeedbackonthiscodebyalsocodingtheirthoughts.

Testing[edit]

Mainarticle:

Test-drivendevelopment

Extremeprogramming'

sapproachisthatifalittletestingcaneliminateafewflaws,alotoftestingcaneliminatemanymoreflaws.

∙Unittestsdeterminewhetheragivenfeatureworksasintended.Aprogrammerwritesasmanyautomatedtestsastheycanthinkofthatmight"

break"

thecode;

ifalltestsrunsuccessfully,thenthecodingiscomplete.Everypieceofcodethatiswrittenistestedbeforemovingontothenextfeature.

∙Acceptancetestsverifythattherequirementsasunderstoodbytheprogrammerssatisfythecustomer'

sactualrequirements.

System-wideintegrationtestingwasencouraged,initially,asadailyend-of-dayactivity,forearlydetectionofincompatibleinterfaces,toreconnectbeforetheseparatesectionsdivergedwidelyfromcoherentfunctionality.However,system-wideintegrationtestinghasbeenreduced,