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Difference between revisions of "EMF Compare FAQ"

(Developpers)
(Redirecting to EMF Compare/FAQ)
 
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=Users=
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#REDIRECT[[EMF_Compare/FAQ]]
====My model is compared as a text-file, how can EMF compare know what file it should handle ?====
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'''Q''' : My model is compared as a text-file, how can EMF compare know what file it should handle ?
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'''A''' : EMF compare uses a content-type to know if it should be started or not. By default this content-type is composed of *.ecore and *.uml file but you may add your own extension using the <tt>Preferences view / Global / Content-types</tt> and adding your file extension in the "Model File" content-type.
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[[Image:EMFComparePreferences-content-type.png]]
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=Developpers=
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====How can I programatically add my model file extension in EMF Compare so that it is called automatically ? ====
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'''Q''' : How can I programatically add my model file extension in EMF Compare so that it is called automatically ?
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'''A''' : Using the "Model File" content-type defined with EMF Compare, here is a sample from a plugin.xml:
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<pre>
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<extension
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        point="org.eclipse.core.contenttype.contentTypes">
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    <file-association
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          content-type="org.eclipse.emf.compare.ui.contenttype.ModelContentType"
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          file-extensions="uml13"
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          file-names="*"/>
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  </extension>
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</pre>
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====Is EMF Compare, as EMF, able to run outside of Eclispe ? ====
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'''Q''' : Is EMF Compare able to compare "in-memory" objects, and can it be run without Eclispe ?
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'''A''': Yes, here is a snippet doing that:
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<pre>
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/**
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* This application will try and launch an headless model comparison.
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*
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* @author Cedric Brun <a href="mailto:cedric.brun@obeo.fr">cedric.brun@obeo.fr</a>
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*/
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public final class ExampleLauncher {
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/**
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* This class doesn't need to be instantiated.
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*/
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private ExampleLauncher() {
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// prevents instantiation
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}
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/**
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* Launcher of this application.
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*
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* @param args
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*            Arguments of the launch.
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*/
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public static void main(String[] args) {
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if (args.length == 2 && new File(args[0]).canRead() && new File(args[1]).canRead()) {
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// Creates the resourceSet where we'll load the models
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final ResourceSet resourceSet = new ResourceSetImpl();
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try {
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// Loads the two models passed as arguments
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final EObject model1 = ModelUtils.load(new File(args[0]), resourceSet);
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final EObject model2 = ModelUtils.load(new File(args[1]), resourceSet);
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// Creates the match then the diff model for those two models
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final MatchModel match = new DifferencesServices().modelMatch(model1, model2, new NullProgressMonitor());
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final DiffModel diff = new DiffMaker().doDiff(match);
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// Prints the results
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try {
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System.out.println(ModelUtils.serialize(match));
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System.out.println(ModelUtils.serialize(diff));
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} catch (IOException e) {
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e.printStackTrace();
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}
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// System.out.println("saving diff as \"result.diff\"");
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// ModelUtils.save(diff, "result.diff");
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// System.out.println("saving match as \"result.match\"");
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// ModelUtils.save(match, "result.match");
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// Serializes the result as "result.emfdiff" in the directory this class has been called from.
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System.out.println("saving emfdiff as \"result.emfdiff\""); //$NON-NLS-1$
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final ModelInputSnapshot snapshot = DiffFactory.eINSTANCE.createModelInputSnapshot();
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snapshot.setDate(Calendar.getInstance().getTime());
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snapshot.setMatch(match);
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snapshot.setDiff(diff);
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ModelUtils.save(snapshot, "result.emfdiff"); //$NON-NLS-1$
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} catch (IOException e) {
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// shouldn't be thrown
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e.printStackTrace();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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} else {
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System.out.println("usage : Launcher <Model1> <Model2>"); //$NON-NLS-1$
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}
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}
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}
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</pre>
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====What kind of "strategies" use EMF compare ? ====
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'''Q''' :  What kind of "strategies" use EMF compare ? On which research work is it based ?
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'''A''' : The emf compare generic engine is based on several research work and on
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experimentations. The paper being the most "near" the emf compare behavior
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is probably "UMLDiff: An Algorithm for Object-OrientedDesign Differencing"
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by Zhenchang Xing and Eleni Stroulia. Other reseach work have been used and
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a lot of them use the same kind of general behavior:
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A comparison in 2 phases, the first being the matching phase and the second
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the differencing phase. The matching is done computing comparison metrics
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and getting an "overall" rank of matching for two nodes while browsing both
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versions of the model. These metrics may change considering the research
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work, here in the generic engine we use 4 metrics :
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*type similarity : analysing the metamodel element
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*name similarity : looking for an attribute which have chances to be the
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name and comparing it
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*value similarity : analysing the whole attributes values
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*relations similarity : using the relations the element has with others.
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Using these 4 metrics the comparison engine provide good correctness (most
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especially comparing models from DSM/DSL's metamodels) and efficiency when
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comparing big models (~=100 000 elements).
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Once the matching phase is done, the matching model is browsed by the
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differencing engine computing "added", "deleted" or updated elements from
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that. If you save a comparison as an emfdiff model you'll be able to browse
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the match and diff model and you'll get the similarity ranking for each
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couple of elements.
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We're open to suggestion to enhance this generic behavior but we are also
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open to other methods : we want this component to be a testbed for other
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algorithms and comparison techniques, any Eclipse plugin may contribute its
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own matching and differencing engine for generic or specific purpose and it
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would be quite interesting to compare the results from different engines on
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different models.
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Latest revision as of 09:48, 26 July 2010

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