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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9.4. <strong>Model</strong>-<strong>Driven</strong>Engineering(RQ3) 197<br />
NormalisationinChapter6wasslightlymoreinvolved.Here,afterthe<br />
bridgebetweenthegrammarware<strong>and</strong>MDAspaces,forwhichwereused<br />
existinggrammarwaretoXML<strong>and</strong>XMLtoMDAbridges,alsosomeabstractionstepswererequired.Wespecifiedtheseabstractionstepsusingmodel<br />
transformations.Hence,thisnormalisationstepwasals<strong>of</strong>ullyautomated.<br />
Inothercasesnormalisationismoredifficult<strong>and</strong>requiresreplacement<br />
<strong>of</strong>customannotations(seeChapter5),theapplication<strong>of</strong>aUMLpr<strong>of</strong>ile,<br />
ortheapplication<strong>of</strong>st<strong>and</strong>ardidiomsforparticularconcerns(seeChapter7).<br />
Thesecasesinvolvemanualeffortfornormalisationthatrequires<br />
domainknowledge. Asanexample,considertheuse<strong>of</strong>UML,ageneralpurposelanguage(GPL),inChapter7.UMLallowstoexpressaparticularconcernusingamultitude<strong>of</strong>differentidioms.<br />
Therefore,additional<br />
constraints<strong>and</strong>modellingconventionsarerequiredtoreducethecomplexity<strong>of</strong>modeltransformations.<br />
Otherwisesuchtransformationshave<br />
totakeintoaccounttoomanypossibleidiomsforaparticularconcern,as<br />
weillustratedinChapter7. Asasolutionweidentifiedtherelevantconcernsinthedomain<strong>of</strong>supervisorymachinecontrol(SMC)systems.<br />
For<br />
eachconcern,wedefinedasinglecorrespondingdesignidiom,whichconformsstrictlytoacorrespondingmetamodel.WedefinedaUML-SMCpr<strong>of</strong>ile,whichconsists<strong>of</strong>stereotypes<strong>and</strong>well-formednessrulesintheObjectConstraintLanguage<br />
1 (OCL)correspondingtothesedesignidioms. Normalisationinvolvesapplyingstereotypestoappropriatemodelelements<strong>and</strong><br />
modifyingthesourcemodelinsuchawaythatconcernsareconsistently<br />
addressedbytheircorrespondingdesignidiomwithoutviolatingany<strong>of</strong>the<br />
well-formednessrules<strong>of</strong>thepr<strong>of</strong>ile.<br />
Forcomplexnormalisations,weidentifiedatrade-<strong>of</strong>fbetweencomplex<br />
transformationrulestoaccountforalargeidiom<strong>of</strong>possibleinputpatterns,<br />
oramoreextensivenormalisationproceduretoaccountforalargenumber<br />
<strong>of</strong>restrictionsonthesourcemodels(i.e.,tolimitthesize<strong>of</strong>thesourcelanguage).<br />
So,evenincaseswherethesource<strong>of</strong>anevolutiontaskisavalidUML<br />
model(i.e.,amodelthatconformstotheUMLmetamodel),normalisation<br />
canberequiredtorestrictthenumber<strong>of</strong>possiblesourceidiomsresultingin<br />
alesscomplexevolutiontransformation.ThiswasnecessaryinChapter7<br />
<strong>and</strong>toalesserextentalsoinChapter5.<br />
TheneedforrestrictingUMLlikethis,raisesthequestionwhetherthe<br />
use<strong>of</strong>aDSMLdefinedusingMOFinsuchcaseswouldn’tbemoreappropriate.Thisisamatter<strong>of</strong>ongoingdebatebetweentwoschools<strong>of</strong>thoughtin<br />
theMDEcommunity[France<strong>and</strong>Rumpe,2007].Onearguesinfavour<strong>of</strong>the<br />
use<strong>of</strong>anextensiblegeneral-purposemodellinglanguage,whiletheother<br />
promotesthedefinition<strong>of</strong>DSMLs.Incurrentpractice,however,thelack<strong>of</strong><br />
1 http://www.omg.org/technology/documents/modeling_spec_catalog.htm#OCL(June2007)
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