Model-Driven Evolution of Software Architectures - Software and ...
Model-Driven Evolution of Software Architectures - Software and ...
Model-Driven Evolution of Software Architectures - Software and ...
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130 Chapter7. <strong>Model</strong>-<strong>Driven</strong>Migration<br />
evolutionarypaths. Consequently, theconformancebetweenthearchitecturespecification<strong>and</strong>s<strong>of</strong>twareimplementationdecreasesasas<strong>of</strong>tware<br />
systemevolves[Briletal.,2005].<br />
Inpractice,increasedcomplexity<strong>and</strong>loss<strong>of</strong>conformancebetweenthe<br />
architectureasintended<strong>and</strong>thearchitectureasimplementedmakeasystemmoredifficulttochange[Perry<strong>and</strong>Wolf,1992].<br />
Thisresultsinan<br />
increase<strong>of</strong>bothdevelopment<strong>and</strong>maintenanceeffort. Theinvolvedeffortcan,forinstance,bereducedbytheseparation<strong>of</strong>concerns,theuse<strong>of</strong><br />
product-linearchitectures,model-drivendevelopment<strong>and</strong>automaticcode<br />
generation.<br />
In this chapter we consider the migration <strong>of</strong> supervisory machine<br />
control(SMC)architecturestowardsaproduct-lineapproachthat,amongst<br />
others,supportsmodel-drivendevelopment<strong>and</strong>codegeneration. Inpractice,<br />
adopting such techniques requires architectural changes. When<br />
migratingtowardsaproductline,suchamigrationneedstobeappliedrepeatedlytomigratedifferentproductversionsintoproduct-linemembers.<br />
Therefore,ideally,onewouldliketomakesuchamigrationreproducibleby<br />
automaticallytransformingonearchitectureintoanother.Inthischapter<br />
weinvestigatehowthiscanbedoneusingmodeltransformations. Developingamodel-drivenmigrationapproachisparticularlybeneficialina<br />
settingwhereproductmigrationisnotaone-<strong>of</strong>fexercise.<br />
Inanadvancedmanufacturingmachine,supervisorycontrol [Ramadge<br />
<strong>and</strong>Wonham,1987;Gohari<strong>and</strong>Wonham,2003]isresponsibleforthecoordination<strong>of</strong>the(discrete)high-levelmachinebehaviour.<br />
Thisrequires,<br />
amongstothers, interpretation<strong>of</strong>manufacturingrequests, synchronisation,<br />
scheduling, conditionalexecution, <strong>and</strong>exploitation<strong>of</strong>concurrency<br />
withrespecttotheresultingmanufacturingactivities [Sabuncuoglu<strong>and</strong><br />
Bayiz,2000;Buttazzo,2002;Reveliotis,2005]. Foradvancedmanufacturingmachines,thecontrolsystemshaveanindicativeorder<strong>of</strong>magnitude<strong>of</strong><br />
10SMCcomponents,eachencompassing10 4 -10 5 lines<strong>of</strong>code.<br />
Thischapterwasmotivatedbytheprototypemigration<strong>of</strong>theSMCarchitecture<strong>of</strong>awaferscannerasdevelopedbyASML,amanufacturer<strong>of</strong>equipmentforthesemiconductorindustry.Weusethiswaferscannerasarunningexampletoillustratethemigration<strong>of</strong>alegacyarchitecture,basedonfinitestatemachines(FSMs),toanewarchitecturethatisbasedontaskresourcesystems(TRSs).ThismigrationisspurredbythefactthataTRSbased<br />
SMCarchitecture,asopposedtoan FSM-basedone,isdeclarative,<br />
separatesconcerns,<strong>and</strong>supportsrun-timedependentdecisions [V<strong>and</strong>en<br />
Nieuwelaar,2004]. Asaresult,themaintainability<strong>and</strong>flexibility<strong>of</strong>the<br />
migrateds<strong>of</strong>twaresystemsisimproved.<br />
Weconsiderthestart<strong>and</strong>endpoint<strong>of</strong>themigrationasdifferentarchitecturalviews[IEEE-1471,2000].<br />
Werefertotheseviewsasthesource<br />
<strong>and</strong>targetviewrespectively. Animportantelement<strong>of</strong>anarchitectural
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