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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158 Chapter7. <strong>Model</strong>-<strong>Driven</strong>Migration<br />
helper context UML!StateVertex def: getPredecessors:Set(UML!<br />
<strong>Model</strong>Element) =<br />
if self.incoming->isEmpty() then<br />
Set{}<br />
else if self.isOrTaskStateJoin then<br />
self.getFork.outgoing->collect(e|e.guard)->select(e|e.<br />
isOrTaskGuard)<br />
else if self.incoming->collect(e|e.guard)->select(e|not e.<br />
oclIsUndefined())->exists(e|e.isOrTaskGuard or if e.oppositeGuard.<br />
oclIsUndefined() then false else e.oppositeGuard.isOrTaskGuard<br />
endif) then<br />
Set{}<br />
else if self.incoming->collect(e|e.source)->select(e|e.isTaskState)<br />
->isEmpty() then<br />
self.incoming->collect(e|e.source.getPredecessors)->flatten()<br />
else<br />
self.incoming->collect(e|e.source)->select(e|e.isTaskState)<br />
endif endif endif endif;<br />
Listing 7.6:CollectpredecessorsonStateVertex<br />
thefiniteset<strong>of</strong>alldirectprecedingmodellingelementsthatmaymaptoa<br />
task.<br />
Concurrentexecution Thenormalisedpatternforconcurrency,asdiscussed<br />
inSection7.6,isaCompositeStatewithorthogonalregions.Toaddressthe<br />
concurrentexecutionconcernweneedtoidentifyinstances<strong>of</strong>suchpatterns<br />
inthesourcemodel.<br />
WedefinedatransformationrulethatcreatesanAndTaskforeveryconcurrentCompositeStateinthesourcemodelexceptforthetopComposite-State<strong>of</strong>theStateMachine.Basically,thepredecessorsrelationisthemechanismusedinthetargetmodelto(dis)allowconcurrency:iftwotasksare<br />
notrelatedbythetransitiveclosure<strong>of</strong>thepredecessorsrelation,theycan<br />
executeconcurrently.Now,thesepotentiallyconcurrenttasksareexecuted<br />
assoonasexecution<strong>of</strong>theirpredecessorshasfinished<strong>and</strong>therequired<br />
resourcesareavailable.Inturn,thisalsoimpliesthatataskcanhavemultiple(concurrent)predecessors.<br />
Collectingpredecessortaskswasalready<br />
discussedinthepreviousparagraph.<br />
ConditionalExecution AsdiscussedinSection7.6, thenormalisedsource<br />
modelusesastatewithtwooutgoingguardedtransitionstospecifyconditionalexecution.Everytwoalternativeconditionalbranchesinasource<br />
modelaremappedtoanOrTaskinthetargetmodel.ThisOrTaskcontains<br />
twosubtasks(iftrue<strong>and</strong>iffalse),whichmaybecomposite<strong>and</strong>representthe<br />
twoconditionallyexecutedbranchesfollowingaStatewithtwooutgoing
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