Why and how to control cloning in software artifacts [Elektronische Ressource] / Elmar Juergens

Juergens

Description

WhyandHowtoControlCloninginSoftwareArtifactsElmar JuergensInstitutfürInformatikderTechnischenUniversitätMünchenWhyandHowtoControlCloninginSoftwareArtifactsElmarJuergensVollständiger Abdruck der von der Fakultät für Informatik der Technischen UniversitätMünchenzurErlangungdesakademischenGradeseinesDoktorsderNaturwissenschaften(Dr.rer.nat.)genehmigtenDissertation.Vorsitzender: Univ.-Prof. BerndBrügge,Ph.D.PrüferderDissertation:1. Univ.-Prof. Dr. Dr. h.c. ManfredBroy2. Univ.-Prof. Dr. RainerKoschkeUniversitätBremenDieDissertationwurdeam07.10.2010beiderTechnischenUniversitätMüncheneingere-ichtunddurchdieFakultätfürInformatikam19.02.2011angenommen.AbstractThe majority of the total life cycle costs of long-lived software arises after its first release, duringsoftwaremaintenance. Cloning,theduplicationofpartsofsoftwareartifacts,hindersmaintenance:it increases size, and thus effort for activities such as inspections and impact analysis. Changesneed to be performed to all clones, instead of to a single location only, thus increasing effort. Ifindividual clones are forgotten during a modification, the resulting inconsistencies can threatenprogramcorrectness. Cloningisthusaqualitydefect.The software engineering community has recognized the negative consequences of cloning overa decade ago. Nevertheless, it abounds in practice—across artifacts, organizations and domains.Cloning thrives, since its control is not part of software engineering practice.

Sujets

• Wissenschaft

Informations

• Publié par: technische_universitat_munchen
• Publié le: 01 janvier 2011
• Nombre de lectures: 18
• Langue: English
• Poids de l'ouvrage: 3 Mo

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ElmarensguerJ

VollständigerAbdruckdervonderFakultätfürInformatikderTechnischenUniversität
MünchenzurErlangungdesakademischenGradeseines

DoktorsderNaturwissenschaften(Dr.rer.nat.)

Dissertation.genehmigten

Vorsitzender:Univ.-Prof.BerndBrügge,Ph.D.
Dissertation:derPrüfer1.Univ.-Prof.Dr.Dr.h.c.Manfred
2.Univ.-Prof.Dr.RainerKoschke

Univ.-Prof.Dr.Dr.h.c.ManfredBroy
Univ.-Prof.Dr.RainerKoschke
BremenersitätvUni

DieDissertationwurdeam07.10.2010beiderTechnischenUniversitätMüncheneingere-
ichtunddurchdieFakultätfürInformatikam19.02.2011angenommen.

Abstract

Themajorityofthetotallifecyclecostsoflong-livedsoftwarearisesafterits®rstrelease,during
softwaremaintenance.Cloning,theduplicationofpartsofsoftwareartifacts,hindersmaintenance:
itincreasessize,andthuseffortforactivitiessuchasinspectionsandimpactanalysis.Changes
needtobeperformedtoallclones,insteadoftoasinglelocationonly,thusincreasingeffort.If
individualclonesareforgottenduringamodi®cation,theresultinginconsistenciescanthreaten
programcorrectness.Cloningisthusaqualitydefect.
Thesoftwareengineeringcommunityhasrecognizedthenegativeconsequencesofcloningover
adecadeago.Nevertheless,itaboundsinpractice—acrossartifacts,organizationsanddomains.
Cloningthrives,sinceitscontrolisnotpartofsoftwareengineeringpractice.Weareconvinced
thatthishastwoprincipalreasons:®rst,thesigni®canceofcloningisnotwellunderstood.We
donotknowtheextentofcloningacrossdifferentartifacttypesandthequantitativeimpactithas
onprogramcorrectnessandmaintenanceefforts.Consequently,wedonotknowtheimportanceof
clonecontrol.Second,nocomprehensivemethodexiststhatguidespractitionersthroughtailoring
andorganizationalchangemanagementrequiredtoestablishsuccessfulclonecontrol.Lackingboth
aquantitativeunderstandingofitsharmfulnessandcomprehensivemethodsforitscontrol,cloning
islikelytobeneglectedinpractice.
Thisthesiscontributestobothareas.First,wepresentempiricalresultsonthesigni®canceof
cloning.Analysisofdifferencesbetweencodeclonesinproductivesoftwarerevealedover100
faults.Morespeci®cally,everysecondmodi®cationtocodethatwasdoneinunawarenessofits
clonescausedafault,demonstratingtheimpactofcodecloningonprogramcorrectness.Further-
more,analysisofindustrialrequirementsspeci®cationsandgraph-basedmodelsrevealedsubstantial
amountsofcloningintheseartifacts,aswell.Thesizeincreasecausedbycloningaffectsinspection
efforts—foronespeci®cation,byanestimated14persondays;forasecondonebyover50%.To
avoidsuchimpactonprogramcorrectnessandmaintenanceefforts,cloningmustbecontrolled.
Second,wepresentacomprehensivemethodforclonecontrol.Itcomprisesdetectortailoringtoim-
proveaccuracyofdetectedclones,andassessmenttoquantifytheirimpact.Itguidesorganizational
changemanagementtosuccessfullyintegrateclonecontrolintoestablishedmaintenanceprocesses,
androotcauseanalysistopreventthecreationofnewclones.Tooperationalizethemethod,we
presentaclonedetectionworkbenchforcode,requirementsspeci®cationsandmodelsthatsupports
allthesesteps.Wedemonstratetheeffectivenessofthemethod—includingitstools—throughan
industrialcasestudy,whereitsuccessfullyreducedcloningintheparticipatingsystem.
Finally,weidentifythelimitationsofclonedetectionandcontrol.Throughacontrolledexperiment,
weshowthatclonedetectionapproachesareunsuitedtodetectbehaviorallysimilarcodethathas
beendevelopedindependentlyandisthusnottheresultofcopy&paste.Itsdetectionremainsan
importanttopicforfuturework.

3

ementswledgknoAc

IhavespentthelastfouryearsasaresearcherattheLehrstuhlforSoftware&SystemsEngineering
atTechnischeUniversitätMünchenfromProf.Dr.Dr.h.c.ManfredBroy.Iwanttoexpressmy
gratitudetoManfredBroyforthefreedomandresponsibilityIwasgrantedandforhisguidanceand
advice.Ihave,andstilldo,enjoyworkinginthechallengingandcompetitiveresearchenvironment
hecreates.IwanttothankProf.Dr.rer.nat.RainerKoschkeforacceptingtoco-supervisethis
thesis.Iamgratefulforinspiringdiscussionsonsoftwarecloning,butalsoforthehospitalityand
interest—bothbyhimandhisgroup—thatIexperiencedduringmyvisitinBremen.Myviewofthe
socialaspectsofresearch,whichformedinthelarge,thematicallyheterogenousgroupofManfred
Broy,wasenrichedbytheglimpseintothesmaller,morefocussedgroupofRainerKoschke.
Iamverygratefultomycolleagues.Theirsupport,bothonthescienti®candonthepersonallevel,
wasvitalforthesuccessofthisthesis.Andnotleast,formypersonaldevelopmentduringthelast
fouryears.IamgratefultoSilkeMüllerforschedulemagic.ToFlorianDeissenboeckforbeing
anexampleworthfollowingandforbothhisencouragementandoutrightcriticism.ToBenjamin
Hummelforhismeritandcreativityinproducingideas,andforhisproductivityandeffectivenessin
theirrealization.ToMartinFeilkasforhisabilitytooverviewandsimplifycomplicatedsituations
andforreliabilityandtrustcomewhatmay.ToStefanWagnerforhisguidanceandexamplein
scienti®cwritingandempiricalresearch.ToDanielRatiuforthesensitivity,carefulnessanddepth
heshowsduringscienti®cdiscussions(andoutsideofthem).ToLarsHeinemannforbeingthebest
colleagueIeversharedanof®cewithandforhistoleranceexhibiteddoingso.ToMarkusHer-
rmannsdörferforhisencouragementandpragmatic,uncomplicatedwaythatmakescollaboration
productiveandfun.ToMarkusPizkaforraisingmyinterestinresearchandforencouragingmeto
startmyPhDthesis.Workingwithallofyouwas,andstillis,aprivilege.
Research,understandingandideagenerationbene®tfromcollaboration.Iamgratefulforjoint
paperprojectstoSebastianBenz,MichaelConradt,FlorianDeissenboeck,ChristophDomann,
MartinFeilkas,Jean-FrançoisGirard,NilsGöde,LarsHeinemann,BenjaminHummel,Klaus
Lochmann,BenediktMayyParareda,MichaelPfaehler,MarkusPizka,DanielRatiu,Bernhard
Schaetz,JonathanStreit,StefanTeuchertandStefanWagner.Inaddition,thisthesisbene®tedfrom
thefeedbackofmany.Iamthankfulforproof-readingdraftstoFlorianDeissenboeck,Martin
Feilkas,NilsGöde,LarsHeinemann,BenjaminHummel,KlausLochmann,BirgitPenzenstadler,
DanielRatiuandStefanWagner.AndtoRebeccaTiarksforhelpwiththeBellonBenchmark.
Theempiricalpartsofthisworkcouldnothavebeenrealizedwithoutthecontinuoussupportofour
industrialpartners.IwanttothankeverybodyIworkedwithatABB,MAN,LV1871andMunich
ReGroup.IparticularlythankMunichReGroup—especiallyRainerJanßenandRudolfVaas—for
thelong-termcollaborationwithourgroupthatsubstantiallysupportedthisdissertation.
Mostofall,Iwanttothankmyfamilyfortheirunconditionalsupport(bothmaterialandimmaterial)
notonlyduringmydissertation,butduringallofmyeducation.Iamdeeplygratefultomyparents,
mybrotherand,aboveall,mywifeSo®e.

5

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John»Aman’CleesesingottaMontydowhatPython’asman’sGuidegottatoLifedo«

Contents

oductionIntr11.1ProblemStatement..................................
1.2Contribution......................................
1.3Contents........................................
Fundamentals22.1NotionsofRedundancy................................
2.2SoftwareCloning...................................
2.3NotionsofProgramSimilarity............................
2.4TermsandDe®nitions.................................
2.5CloneMetrics.....................................
2.6Data-¯owModels...................................
2.7CaseStudyPartners..................................
2.8Summary.......................................
3StateoftheArt
3.1ImpactonProgramCorrectness............................
3.2ExtentofCloning...................................
3.3CloneDetectionApproaches.............................
3.4CloneAssessmentandManagement.........................
3.5LimitationsofCloneDetection............................
4ImpactonProgramCorrectness
4.1ResearchQuestions..................................
4.2StudyDesign.....................................
4.3StudyObjects.....................................
4.4ImplementationandExecution............................
4.5Results.........................................
4.6Discussion.......................................
4.7ThreatstoValidity...................................
4.8Summary.......................................
5CloningBeyondCode
5.1ResearchQuestions..................................
5.2StudyDesign.....................................
5.3StudyObjects.....................................
5.4ImplementationandExecution............................

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Contents

5.5Results.........................................68
5.6Discussion.......................................76
5.7ThreatstoValidity...................................77
5.8Summary.......................................79
81ModelCostClone66.1MaintenanceProcess.................................81
6.2Approach.......................................83
6.3DetailedCostModel.................................84
6.4Simpli®edCostModel................................8