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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6.6. Discussion 123<br />
addition<strong>of</strong>additionaltypes<strong>of</strong>connectorsordependencyrelations.Ifsuch<br />
additionsdonotrequireaspecificapproachforcomparison<strong>and</strong>presentation,thetransformationswespecifiedcanstillbeapplied.<br />
6.6.2 ImprovingtheApproach<br />
Generalisation Theuse<strong>of</strong>ATLmakesourapproachspecifictotheMDAtechnologicalspace.<br />
Thismeansthatwerequiresourcemodelstoconformto<br />
aMOF-basedmetamodel<strong>and</strong>tobeserialisedwithXMI. Inprinciplethis<br />
makesourapproachcompatiblewithmostUMLtools(viaXMI).However,in<br />
practiceadditionaltransformationsare<strong>of</strong>tenrequiredtoexchangesource<br />
<strong>and</strong>targetmodelsbetweenmodelling, visualisation<strong>and</strong>transformation<br />
tools(seealsoSections5.7<strong>and</strong>7.9).<br />
Thespecification<strong>of</strong>modelpopulationtransformationsisdependenton<br />
theapplied(programming<strong>and</strong>modelling)style(e.g.,usage<strong>of</strong>patterns<strong>and</strong><br />
codingconventions).Therequiredcomplexity<strong>of</strong>transformationrulesalso<br />
dependsontheprogrammingstyle. Forinstance,theuse<strong>of</strong>getter<strong>and</strong><br />
settermethodscircumventstheneedtolookfordirectfieldaccess.<br />
Togeneralisethecomparisonstep<strong>of</strong>ourapproachweconsideredthe<br />
definition<strong>of</strong>acompletegenericmetamodelfor(conformance)views.Sucha<br />
metamodelwoulddefineadditionalViewParts(seeFigure6.5onpage111)<br />
suchasElement,ConnectingElement,<strong>and</strong>Relation.TheseViewPartscan<br />
thenbespecialisedbymetamodelsforparticularviewpoints.Forexample,<br />
intheCPADLmetamodelaConnectorwouldbeaConnectingElement,<strong>and</strong><br />
anAttachmentaRelation.Allthiswouldmakesensewhenitispossibleto<br />
specifytransformationsforcomparison<strong>and</strong>presentationinterms<strong>of</strong>those<br />
genericViewParts. Thesetransformationscanthenbeusedforarbitrary<br />
conformancemodels.Theproblemwiththisapproachisthatitisnotpossibletoalsodefinegenericrelationsbetweenmetamodelelementsthatcanbe<br />
specialisedbyaconcretemetamodel.Soalthoughitispossibletodevelopa<br />
transformationtoalwayspresentaConnectingElementasanellipse,such<br />
atransformationcannotalsoinstantiateitsrelationsinagenericway.<br />
Wecanovercomethisproblembytheuse<strong>of</strong>higher-ordertransformations.<br />
Thesearetransformationsthathaveanothertransformationas<br />
sourceortargetmodel.ForATLthisismadepossiblebytheavailability<strong>of</strong><br />
ametamodelformodel-basedrepresentation<strong>of</strong>ATLtransformations<strong>and</strong><br />
correspondingprojectors. Suchahigher-ordertransformationwouldtake<br />
themetamodelinvolvedintheconformancecheckassourcemodel<strong>and</strong><br />
produceamodel<strong>of</strong>thetransformationsforcomparison<strong>and</strong>presentation<strong>of</strong><br />
theassociatedmodels.Thisappearstobefeasibleconsideringthefactthat<br />
thetransformationsweimplementedforthosestepsarequitesimilar.<br />
ThisapproachisinvestigatedinGraaf<strong>and</strong>vanDeursen[2007b],where<br />
weprovideamoreextensivegenericmetamodel,asdiscussedabove.Based
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