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Difference between revisions of "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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[[Category:FAQ]]
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#REDIRECT[[EMF_Compare/FAQ]]
 
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=Users=
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====Which files should be compared via EMF Compare ?====
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'''Q''' : My model is compared as a text-file, how can EMF compare know the files it should handle ?
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'''A''' : EMF compare uses a content-type to know whether it should be used for comparison. This content-type will initially register itself against *.ecore and *.uml files. You may add your own extension using the <tt>Preferences view / Global / Content-types</tt> and adding your file extension in the "EMF Compare" content-type.
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[[Image:EMFComparePreferences-content-type.png]]
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====How to force text comparison?====
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'''Q''' : uml, ecore and emfdiff models are "locked" as model files in the aforementioned "Model File" content-type. I want to compare two uml files as text, is there a way to do so?
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'''A''' : You can force text comparison of those "locked" model files by adding their extension to the "text" content type in the same way as what is explained above.
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====Is EMF Compare compatible with the JDK 1.4?====
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'''Q''' : Will EMF Compare work with JDK 1.4?
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'''A''' : EMF Compare is built against JDK 1.5 and makes use of the features it introduced such as foreach and generics. It is therefore incompatible with a JDK < 1.5.
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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 Eclipse ? ====
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'''Q''' : Is EMF Compare able to compare "in-memory" objects, and can it be run without Eclipse ?
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'''A''': Yes, [http://wiki.eclipse.org/images/2/23/Org.eclipse.emf.compare.example.standalone-I200710230727.zip here] is a Java project example doing just that.
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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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These strategies will probably evolve in the next releases (see following question).
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====What evolution should we expect on the global EMF compare strategies ? ====
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'''Q''' :  What evolution should we expect on the global EMF compare strategies ?
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'''A''' : We are trying to get better results with generic comparison algorithm through other methods coming from the research world. An initiative about model transformation/weaving and comparison is taking place in Europe an you may expect that the EMF compare implementation will evolve toward these works.
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[http://www.model-transformation.org/ Model Transformation initiative]
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Latest revision as of 09:48, 26 July 2010

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