[403055] Provide a match engine extension mechanism.

Make the match engine extensible by providing extension point mechanism.

Bug: 403055
Change-Id: I5b824adf66840d76b8046518103d447ad5711c41

17 files changed, 2361 insertions, 1551 deletions

diff --git a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/handler/AbstractCompareHandler.java b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/handler/AbstractCompareHandler.java
index 0bc0416c7..a327dec19 100644
--- a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/handler/AbstractCompareHandler.java
+++ b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/handler/AbstractCompareHandler.java
@@ -1,140 +1,204 @@
-/*******************************************************************************

- * Copyright (c) 2012, 2013 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- * 

- * Contributors:

- *     Obeo - initial API and implementation

- *******************************************************************************/

-package org.eclipse.emf.compare.ide.ui.internal.handler;

-

-import com.google.common.collect.Iterators;

-

-import java.util.Iterator;

-

-import org.eclipse.compare.CompareConfiguration;

-import org.eclipse.compare.CompareEditorInput;

-import org.eclipse.core.commands.AbstractHandler;

-import org.eclipse.emf.common.command.CommandStack;

-import org.eclipse.emf.common.notify.AdapterFactory;

-import org.eclipse.emf.common.notify.Notifier;

-import org.eclipse.emf.common.util.Monitor;

-import org.eclipse.emf.compare.CompareFactory;

-import org.eclipse.emf.compare.Comparison;

-import org.eclipse.emf.compare.EMFCompare;

-import org.eclipse.emf.compare.Match;

-import org.eclipse.emf.compare.domain.ICompareEditingDomain;

-import org.eclipse.emf.compare.domain.impl.EMFCompareEditingDomain;

-import org.eclipse.emf.compare.ide.ui.internal.editor.ComparisonScopeEditorInput;

-import org.eclipse.emf.compare.match.DefaultComparisonFactory;

-import org.eclipse.emf.compare.match.DefaultEqualityHelperFactory;

-import org.eclipse.emf.compare.match.DefaultMatchEngine;

-import org.eclipse.emf.compare.match.IComparisonFactory;

-import org.eclipse.emf.compare.match.IMatchEngine;

-import org.eclipse.emf.compare.match.eobject.IEObjectMatcher;

-import org.eclipse.emf.compare.provider.AdapterFactoryUtil;

-import org.eclipse.emf.compare.rcp.EMFCompareRCPPlugin;

-import org.eclipse.emf.compare.scope.IComparisonScope;

-import org.eclipse.emf.compare.utils.UseIdentifiers;

-import org.eclipse.emf.ecore.EObject;

-import org.eclipse.emf.edit.domain.AdapterFactoryEditingDomain;

-import org.eclipse.emf.edit.domain.EditingDomain;

-import org.eclipse.emf.edit.domain.IEditingDomainProvider;

-import org.eclipse.ui.IWorkbenchPart;

-

-/**

- * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>

- */

-public abstract class AbstractCompareHandler extends AbstractHandler {

-

-	protected static CompareEditorInput createCompareEditorInput(IWorkbenchPart part,

-			AdapterFactory adapterFactory, Notifier left, Notifier right, Notifier origin) {

-		CompareEditorInput input = null;

-

-		ICompareEditingDomain editingDomain = createEMFCompareEditingDomain(part, left, right, origin);

-

-		final CompareConfiguration configuration = new CompareConfiguration();

-		// never use id in EObjects comparison

-		IEObjectMatcher eObjectMatcher = DefaultMatchEngine.createDefaultEObjectMatcher(UseIdentifiers.NEVER);

-		IMatchEngine matchEngine = new MatchEObjectEngine(eObjectMatcher, new DefaultComparisonFactory(

-				new DefaultEqualityHelperFactory()));

-		EMFCompare comparator = EMFCompare.builder().setMatchEngine(matchEngine).setPostProcessorRegistry(

-				EMFCompareRCPPlugin.getDefault().getPostProcessorRegistry()).build();

-		IComparisonScope scope = EMFCompare.createDefaultScope(left, right, origin);

-		input = new ComparisonScopeEditorInput(configuration, editingDomain, adapterFactory, comparator,

-				scope);

-

-		input.setTitle("Compare ('" + AdapterFactoryUtil.getText(adapterFactory, left) + "' - '"

-				+ AdapterFactoryUtil.getText(adapterFactory, right) + "')");

-

-		configuration.setContainer(input);

-		return input;

-	}

-

-	private static ICompareEditingDomain createEMFCompareEditingDomain(final IWorkbenchPart activePart,

-			final Notifier left, final Notifier right, Notifier origin) {

-

-		EditingDomain delegatingEditingDomain = getDelegatingEditingDomain(activePart, left, right);

-		CommandStack delegatingCommandStack = null;

-		if (delegatingEditingDomain != null) {

-			delegatingCommandStack = delegatingEditingDomain.getCommandStack();

-		}

-

-		return EMFCompareEditingDomain.create(left, right, origin, delegatingCommandStack);

-	}

-

-	private static EditingDomain getDelegatingEditingDomain(final IWorkbenchPart activePart, Notifier left,

-			Notifier right) {

-		EditingDomain delegatingEditingDomain = null;

-		if (activePart instanceof IEditingDomainProvider) {

-			delegatingEditingDomain = ((IEditingDomainProvider)activePart).getEditingDomain();

-		} else if (AdapterFactoryEditingDomain.getEditingDomainFor(left) != null) {

-			EditingDomain leftEditingDomain = AdapterFactoryEditingDomain.getEditingDomainFor(left);

-			EditingDomain rightEditingDomain = AdapterFactoryEditingDomain.getEditingDomainFor(right);

-			// do not use a delegating editing domain if those two are different.

-			if (leftEditingDomain == rightEditingDomain) {

-				delegatingEditingDomain = AdapterFactoryEditingDomain.getEditingDomainFor(left);

-			}

-		}

-		return delegatingEditingDomain;

-	}

-

-	private static class MatchEObjectEngine extends DefaultMatchEngine {

-		/**

-		 * @param matcher

-		 * @param comparisonFactory

-		 */

-		public MatchEObjectEngine(IEObjectMatcher matcher, IComparisonFactory comparisonFactory) {

-			super(matcher, comparisonFactory);

-		}

-

-		@Override

-		protected void match(Comparison comparison, IComparisonScope scope, EObject left, EObject right,

-				EObject origin, Monitor monitor) {

-			if (left == null || right == null) {

-				throw new IllegalArgumentException();

-			}

-

-			Match rootMatch = CompareFactory.eINSTANCE.createMatch();

-			rootMatch.setLeft(left);

-			rootMatch.setRight(right);

-			rootMatch.setOrigin(origin);

-			comparison.getMatches().add(rootMatch);

-

-			final Iterator<? extends EObject> leftEObjects = scope.getChildren(left);

-			final Iterator<? extends EObject> rightEObjects = scope.getChildren(right);

-			final Iterator<? extends EObject> originEObjects;

-			if (origin != null) {

-				originEObjects = scope.getChildren(origin);

-			} else {

-				originEObjects = Iterators.emptyIterator();

-			}

-

-			getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects,

-					monitor);

-

-		}

-	}

-}

+/*******************************************************************************
+ * Copyright (c) 2012, 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.ide.ui.internal.handler;
+
+import com.google.common.collect.Iterators;
+
+import java.util.Iterator;
+
+import org.eclipse.compare.CompareConfiguration;
+import org.eclipse.compare.CompareEditorInput;
+import org.eclipse.core.commands.AbstractHandler;
+import org.eclipse.emf.common.command.CommandStack;
+import org.eclipse.emf.common.notify.AdapterFactory;
+import org.eclipse.emf.common.notify.Notifier;
+import org.eclipse.emf.common.util.Monitor;
+import org.eclipse.emf.compare.CompareFactory;
+import org.eclipse.emf.compare.Comparison;
+import org.eclipse.emf.compare.EMFCompare;
+import org.eclipse.emf.compare.Match;
+import org.eclipse.emf.compare.domain.ICompareEditingDomain;
+import org.eclipse.emf.compare.domain.impl.EMFCompareEditingDomain;
+import org.eclipse.emf.compare.ide.ui.internal.editor.ComparisonScopeEditorInput;
+import org.eclipse.emf.compare.match.DefaultComparisonFactory;
+import org.eclipse.emf.compare.match.DefaultEqualityHelperFactory;
+import org.eclipse.emf.compare.match.DefaultMatchEngine;
+import org.eclipse.emf.compare.match.IComparisonFactory;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.match.eobject.IEObjectMatcher;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryImpl;
+import org.eclipse.emf.compare.provider.AdapterFactoryUtil;
+import org.eclipse.emf.compare.rcp.EMFCompareRCPPlugin;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+import org.eclipse.emf.compare.utils.UseIdentifiers;
+import org.eclipse.emf.ecore.EObject;
+import org.eclipse.emf.edit.domain.AdapterFactoryEditingDomain;
+import org.eclipse.emf.edit.domain.EditingDomain;
+import org.eclipse.emf.edit.domain.IEditingDomainProvider;
+import org.eclipse.ui.IWorkbenchPart;
+
+/**
+ * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>
+ */
+public abstract class AbstractCompareHandler extends AbstractHandler {
+
+	protected static CompareEditorInput createCompareEditorInput(IWorkbenchPart part,
+			AdapterFactory adapterFactory, Notifier left, Notifier right, Notifier origin) {
+		CompareEditorInput input = null;
+
+		ICompareEditingDomain editingDomain = createEMFCompareEditingDomain(part, left, right, origin);
+
+		final CompareConfiguration configuration = new CompareConfiguration();
+		IMatchEngine.Factory eObjectMatchEngineFactory = new MatchEObjectEngineFactory();
+		eObjectMatchEngineFactory.setRanking(9);
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = EMFCompareRCPPlugin.getDefault()
+				.getMatchEngineFactoryRegistry();
+		matchEngineFactoryRegistry.add(eObjectMatchEngineFactory);
+
+		EMFCompare comparator = EMFCompare.builder()
+				.setMatchEngineFactoryRegistry(matchEngineFactoryRegistry).setPostProcessorRegistry(
+						EMFCompareRCPPlugin.getDefault().getPostProcessorRegistry()).build();
+		IComparisonScope scope = EMFCompare.createDefaultScope(left, right, origin);
+		input = new ComparisonScopeEditorInput(configuration, editingDomain, adapterFactory, comparator,
+				scope);
+
+		input.setTitle("Compare ('" + AdapterFactoryUtil.getText(adapterFactory, left) + "' - '"
+				+ AdapterFactoryUtil.getText(adapterFactory, right) + "')");
+
+		configuration.setContainer(input);
+		return input;
+	}
+
+	private static ICompareEditingDomain createEMFCompareEditingDomain(final IWorkbenchPart activePart,
+			final Notifier left, final Notifier right, Notifier origin) {
+
+		EditingDomain delegatingEditingDomain = getDelegatingEditingDomain(activePart, left, right);
+		CommandStack delegatingCommandStack = null;
+		if (delegatingEditingDomain != null) {
+			delegatingCommandStack = delegatingEditingDomain.getCommandStack();
+		}
+
+		return EMFCompareEditingDomain.create(left, right, origin, delegatingCommandStack);
+	}
+
+	private static EditingDomain getDelegatingEditingDomain(final IWorkbenchPart activePart, Notifier left,
+			Notifier right) {
+		EditingDomain delegatingEditingDomain = null;
+		if (activePart instanceof IEditingDomainProvider) {
+			delegatingEditingDomain = ((IEditingDomainProvider)activePart).getEditingDomain();
+		} else if (AdapterFactoryEditingDomain.getEditingDomainFor(left) != null) {
+			EditingDomain leftEditingDomain = AdapterFactoryEditingDomain.getEditingDomainFor(left);
+			EditingDomain rightEditingDomain = AdapterFactoryEditingDomain.getEditingDomainFor(right);
+			// do not use a delegating editing domain if those two are different.
+			if (leftEditingDomain == rightEditingDomain) {
+				delegatingEditingDomain = AdapterFactoryEditingDomain.getEditingDomainFor(left);
+			}
+		}
+		return delegatingEditingDomain;
+	}
+
+	/**
+	 * A specialized {@link MatchEngineFactoryImpl} that wrap a {@link MatchEObjectEngine}.
+	 * 
+	 * @author <a href="mailto:axel.richard@obeo.fr">Axel Richard</a>
+	 */
+	private static class MatchEObjectEngineFactory extends MatchEngineFactoryImpl {
+
+		/**
+		 * Default Constructor.
+		 */
+		public MatchEObjectEngineFactory() {
+			matchEngine = new MatchEObjectEngine();
+		}
+
+		/**
+		 * {@inheritDoc}
+		 * 
+		 * @see 
+		 *      org.eclipse.emf.compare.match.IMatchEngine.Factory.isMatchEngineFactoryFor(org.eclipse.emf.compare
+		 *      .scope.IComparisonScope)
+		 */
+		@Override
+		public boolean isMatchEngineFactoryFor(IComparisonScope scope) {
+			final Notifier left = scope.getLeft();
+			final Notifier right = scope.getRight();
+			if (left instanceof EObject && right instanceof EObject) {
+				return true;
+			}
+			return false;
+		}
+	}
+
+	/**
+	 * A specialized {@link DefaultMatchEngine} for comparison between EObjects.
+	 * 
+	 * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>
+	 */
+	private static class MatchEObjectEngine extends DefaultMatchEngine {
+
+		/**
+		 * Default Constructor.
+		 */
+		public MatchEObjectEngine() {
+			// never use id in EObjects comparison
+			super(DefaultMatchEngine.createDefaultEObjectMatcher(UseIdentifiers.NEVER),
+					new DefaultComparisonFactory(new DefaultEqualityHelperFactory()));
+		}
+
+		/**
+		 * Constructor with matcher and comparison factory parameters.
+		 * 
+		 * @param matcher
+		 *            The matcher that will be in charge of pairing EObjects together for this comparison
+		 *            process.
+		 * @param comparisonFactory
+		 *            factory that will be use to instantiate Comparison as return by match() methods.
+		 */
+		public MatchEObjectEngine(IEObjectMatcher matcher, IComparisonFactory comparisonFactory) {
+			super(matcher, comparisonFactory);
+		}
+
+		/**
+		 * {@inheritDoc}
+		 * 
+		 * @see org.eclipse.emf.compare.match.DefaultMatchEngine.match(org.eclipse.emf.compare.Comparison,
+		 *      org.eclipse.emf.compare.scope.IComparisonScope, org.eclipse.emf.ecore.EObject,
+		 *      org.eclipse.emf.ecore.EObject, org.eclipse.emf.ecore.EObject,
+		 *      org.eclipse.emf.common.util.Monitor)
+		 */
+		@Override
+		protected void match(Comparison comparison, IComparisonScope scope, EObject left, EObject right,
+				EObject origin, Monitor monitor) {
+			if (left == null || right == null) {
+				throw new IllegalArgumentException();
+			}
+
+			Match rootMatch = CompareFactory.eINSTANCE.createMatch();
+			rootMatch.setLeft(left);
+			rootMatch.setRight(right);
+			rootMatch.setOrigin(origin);
+			comparison.getMatches().add(rootMatch);
+
+			final Iterator<? extends EObject> leftEObjects = scope.getChildren(left);
+			final Iterator<? extends EObject> rightEObjects = scope.getChildren(right);
+			final Iterator<? extends EObject> originEObjects;
+			if (origin != null) {
+				originEObjects = scope.getChildren(origin);
+			} else {
+				originEObjects = Iterators.emptyIterator();
+			}
+
+			getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects,
+					monitor);
+
+		}
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java
index 4e65d5cb3..a44e09212 100644
--- a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java
+++ b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/structuremergeviewer/EMFCompareStructureMergeViewer.java
@@ -273,9 +273,12 @@ public class EMFCompareStructureMergeViewer extends DiffTreeViewer implements Co
 				}
 
 				final IComparisonScope scope = syncModel.createMinimizedScope();
-				final Comparison compareResult = EMFCompare.builder().setPostProcessorRegistry(
-						EMFCompareRCPPlugin.getDefault().getPostProcessorRegistry()).build().compare(scope,
-						BasicMonitor.toMonitor(monitor));
+				final Comparison compareResult = EMFCompare
+						.builder()
+						.setMatchEngineFactoryRegistry(
+								EMFCompareRCPPlugin.getDefault().getMatchEngineFactoryRegistry())
+						.setPostProcessorRegistry(EMFCompareRCPPlugin.getDefault().getPostProcessorRegistry())
+						.build().compare(scope, BasicMonitor.toMonitor(monitor));
 
 				final ResourceSet leftResourceSet = (ResourceSet)scope.getLeft();
 				final ResourceSet rightResourceSet = (ResourceSet)scope.getRight();
diff --git a/plugins/org.eclipse.emf.compare.rcp/META-INF/MANIFEST.MF b/plugins/org.eclipse.emf.compare.rcp/META-INF/MANIFEST.MF
index e893c5b74..6e4c0e677 100644
--- a/plugins/org.eclipse.emf.compare.rcp/META-INF/MANIFEST.MF
+++ b/plugins/org.eclipse.emf.compare.rcp/META-INF/MANIFEST.MF
@@ -13,6 +13,7 @@ Bundle-Localization: plugin
 Export-Package: org.eclipse.emf.compare.rcp,
  org.eclipse.emf.compare.rcp.extension,
  org.eclipse.emf.compare.rcp.internal;x-internal:=true,
+ org.eclipse.emf.compare.rcp.internal.match;x-internal:=true,
  org.eclipse.emf.compare.rcp.internal.merger;x-internal:=true,
  org.eclipse.emf.compare.rcp.internal.policy;x-internal:=true,
  org.eclipse.emf.compare.rcp.internal.postprocessor;x-internal:=true,
diff --git a/plugins/org.eclipse.emf.compare.rcp/plugin.xml b/plugins/org.eclipse.emf.compare.rcp/plugin.xml
index a5276bd25..48a8ce2c9 100644
--- a/plugins/org.eclipse.emf.compare.rcp/plugin.xml
+++ b/plugins/org.eclipse.emf.compare.rcp/plugin.xml
@@ -1,50 +1,58 @@
-<?xml version="1.0" encoding="UTF-8"?>

-<?eclipse version="3.4"?>

-

-<!--

- Copyright (c) 2013 Obeo.

- All rights reserved. This program and the accompanying materials

- are made available under the terms of the Eclipse Public License v1.0

- which accompanies this distribution, and is available at

- http://www.eclipse.org/legal/epl-v10.html

- 

- Contributors:

-     Obeo - initial API and implementation

--->

-

-<plugin>

-   <extension-point id="postProcessor" name="Post Processor" schema="schema/postProcessor.exsd"/>

-   <extension-point id="merger" name="Merger" schema="schema/merger.exsd"/>

-   <extension-point id="loadOnDemandPolicy" name="Load on Demand Policy" schema="schema/loadOnDemandPolicy.exsd"/>

-   

-   <extension point="org.eclipse.emf.ecore.generated_package">

-      <package

-            uri="http://www.eclipse.org/emf/compare"

-            class="org.eclipse.emf.compare.ComparePackage"

-            genModel="platform:/plugin/org.eclipse.emf.compare/model/compare.genmodel"/>

-   </extension>

-   

-   <extension

-         point="org.eclipse.emf.compare.rcp.merger">

-      <merger

-            class="org.eclipse.emf.compare.merge.ResourceAttachmentChangeMerger"

-            ranking="10">

-      </merger>

-      <merger

-            class="org.eclipse.emf.compare.merge.ReferenceChangeMerger"

-            ranking="10">

-      </merger>

-      <merger

-            class="org.eclipse.emf.compare.merge.AttributeChangeMerger"

-            ranking="10">

-      </merger>

-   </extension>

-   <extension

-         point="org.eclipse.core.contenttype.contentTypes">

-      <content-type

-            id="org.eclipse.emf.compare.content.type"

-            name="EMF Compare"

-            priority="normal">

-      </content-type>

-   </extension>

-</plugin>

+<?xml version="1.0" encoding="UTF-8"?>
+<?eclipse version="3.4"?>
+
+<!--
+ Copyright (c) 2013 Obeo.
+ All rights reserved. This program and the accompanying materials
+ are made available under the terms of the Eclipse Public License v1.0
+ which accompanies this distribution, and is available at
+ http://www.eclipse.org/legal/epl-v10.html
+ 
+ Contributors:
+     Obeo - initial API and implementation
+-->
+
+<plugin>
+   <extension-point id="postProcessor" name="Post Processor" schema="schema/postProcessor.exsd"/>
+   <extension-point id="merger" name="Merger" schema="schema/merger.exsd"/>
+   <extension-point id="loadOnDemandPolicy" name="Load on Demand Policy" schema="schema/loadOnDemandPolicy.exsd"/>
+   <extension-point id="matchEngine" name="Match Engine" schema="schema/matchEngine.exsd"/>
+   
+   <extension point="org.eclipse.emf.ecore.generated_package">
+      <package
+            uri="http://www.eclipse.org/emf/compare"
+            class="org.eclipse.emf.compare.ComparePackage"
+            genModel="platform:/plugin/org.eclipse.emf.compare/model/compare.genmodel"/>
+   </extension>
+   
+   <extension
+         point="org.eclipse.emf.compare.rcp.merger">
+      <merger
+            class="org.eclipse.emf.compare.merge.ResourceAttachmentChangeMerger"
+            ranking="10">
+      </merger>
+      <merger
+            class="org.eclipse.emf.compare.merge.ReferenceChangeMerger"
+            ranking="10">
+      </merger>
+      <merger
+            class="org.eclipse.emf.compare.merge.AttributeChangeMerger"
+            ranking="10">
+      </merger>
+   </extension>
+   <extension
+         point="org.eclipse.core.contenttype.contentTypes">
+      <content-type
+            id="org.eclipse.emf.compare.content.type"
+            name="EMF Compare"
+            priority="normal">
+      </content-type>
+   </extension>
+   <extension
+         point="org.eclipse.emf.compare.rcp.matchEngine">
+      <engineFactory
+            class="org.eclipse.emf.compare.match.impl.MatchEngineFactoryImpl"
+            ranking="10">
+      </engineFactory>
+   </extension>
+</plugin>
diff --git a/plugins/org.eclipse.emf.compare.rcp/schema/matchEngine.exsd b/plugins/org.eclipse.emf.compare.rcp/schema/matchEngine.exsd
new file mode 100644
index 000000000..2572f4e4c
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.rcp/schema/matchEngine.exsd
@@ -0,0 +1,116 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!-- Schema file written by PDE -->
+<schema targetNamespace="org.eclipse.emf.compare.rcp" xmlns="http://www.w3.org/2001/XMLSchema">
+<annotation>
+      <appinfo>
+         <meta.schema plugin="org.eclipse.emf.compare.rcp" id="matchEngine" name="EMF Compare Match Engine"/>
+      </appinfo>
+      <documentation>
+         This extension point can be used in order to customize the match engine used for comparison.
+      </documentation>
+   </annotation>
+
+   <element name="extension">
+      <annotation>
+         <appinfo>
+            <meta.element />
+         </appinfo>
+      </annotation>
+      <complexType>
+         <sequence>
+            <element ref="engineFactory" minOccurs="1" maxOccurs="unbounded"/>
+         </sequence>
+         <attribute name="point" type="string" use="required">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="id" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+         <attribute name="name" type="string">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+               <appinfo>
+                  <meta.attribute translatable="true"/>
+               </appinfo>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <element name="engineFactory">
+      <complexType>
+         <attribute name="class" type="string" use="required">
+            <annotation>
+               <documentation>
+                  Describes a Match engine Factory and its enablement value.
+               </documentation>
+               <appinfo>
+                  <meta.attribute kind="java" basedOn=":org.eclipse.emf.compare.match.IMatchEngine$Factory"/>
+               </appinfo>
+            </annotation>
+         </attribute>
+         <attribute name="ranking" type="string" use="required">
+            <annotation>
+               <documentation>
+                  
+               </documentation>
+            </annotation>
+         </attribute>
+      </complexType>
+   </element>
+
+   <annotation>
+      <appinfo>
+         <meta.section type="since"/>
+      </appinfo>
+      <documentation>
+         2.1.0
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appinfo>
+         <meta.section type="examples"/>
+      </appinfo>
+      <documentation>
+         &lt;extension point=&quot;org.eclipse.emf.compare.rcp.matchEngine&quot;&gt;
+  &lt;engineFactory class=&quot;org.eclipse.emf.compare.match.impl.MatchEngineFactoryImpl&quot; ranking=&quot;10&quot;/&gt;
+&lt;/extension&gt;
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appinfo>
+         <meta.section type="implementation"/>
+      </appinfo>
+      <documentation>
+         See org.eclipse.emf.compare.rcp/plugin.xml for existing contributions.
+      </documentation>
+   </annotation>
+
+   <annotation>
+      <appinfo>
+         <meta.section type="copyright"/>
+      </appinfo>
+      <documentation>
+         Copyright (c) 2013 Obeo.
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License v1.0
+which accompanies this distribution, and is available at
+http://www.eclipse.org/legal/epl-v10.html
+
+Contributors:
+    Obeo - initial API and implementation
+      </documentation>
+   </annotation>
+</schema>
diff --git a/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/EMFCompareRCPPlugin.java b/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/EMFCompareRCPPlugin.java
index b18adbf6f..6590d9d6d 100644
--- a/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/EMFCompareRCPPlugin.java
+++ b/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/EMFCompareRCPPlugin.java
@@ -14,10 +14,13 @@ import org.eclipse.core.runtime.IExtensionRegistry;
 import org.eclipse.core.runtime.Platform;
 import org.eclipse.core.runtime.Plugin;
 import org.eclipse.core.runtime.Status;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryRegistryImpl;
 import org.eclipse.emf.compare.merge.IMerger;
 import org.eclipse.emf.compare.postprocessor.IPostProcessor;
 import org.eclipse.emf.compare.postprocessor.PostProcessorDescriptorRegistryImpl;
 import org.eclipse.emf.compare.rcp.extension.AbstractRegistryEventListener;
+import org.eclipse.emf.compare.rcp.internal.match.MatchEngineFactoryRegistryListener;
 import org.eclipse.emf.compare.rcp.internal.merger.MergerExtensionRegistryListener;
 import org.eclipse.emf.compare.rcp.internal.policy.LoadOnDemandPolicyRegistryImpl;
 import org.eclipse.emf.compare.rcp.internal.policy.LoadOnDemandPolicyRegistryListener;
@@ -41,6 +44,9 @@ public class EMFCompareRCPPlugin extends Plugin {
 	/** The id of the merger extension point. */
 	public static final String MERGER_PPID = "merger"; //$NON-NLS-1$
 
+	/** The id of the match extension point. */
+	public static final String MATCH_ENGINE_PPID = "matchEngine"; //$NON-NLS-1$
+
 	// This plugin is a singleton, so it's quite ok to keep the plugin in a static field.
 	private static EMFCompareRCPPlugin plugin;
 
@@ -62,6 +68,12 @@ public class EMFCompareRCPPlugin extends Plugin {
 	/** The registry listener that will be used to react to post processor changes. */
 	private AbstractRegistryEventListener postProcessorFactoryRegistryListener;
 
+	/** The registry that will hold references to all match engine factories. */
+	private IMatchEngine.Factory.Registry matchEngineFactoryRegistry;
+
+	/** The registry listener that will be used to react to match engine changes. */
+	private MatchEngineFactoryRegistryListener matchEngineRegistryListener;
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.osgi.framework.BundleActivator#start(org.osgi.framework.BundleContext)
@@ -72,6 +84,11 @@ public class EMFCompareRCPPlugin extends Plugin {
 
 		final IExtensionRegistry registry = Platform.getExtensionRegistry();
 
+		matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineRegistryListener = new MatchEngineFactoryRegistryListener(PLUGIN_ID, MATCH_ENGINE_PPID,
+				getLog(), matchEngineFactoryRegistry);
+		matchEngineRegistryListener.readRegistry(registry);
+
 		mergerRegistry = new IMerger.RegistryImpl();
 		mergerRegistryListener = new MergerExtensionRegistryListener(PLUGIN_ID, MERGER_PPID, getLog(),
 				mergerRegistry);
@@ -112,6 +129,10 @@ public class EMFCompareRCPPlugin extends Plugin {
 		registry.removeListener(mergerRegistryListener);
 		mergerRegistryListener = null;
 		mergerRegistry = null;
+
+		registry.removeListener(matchEngineRegistryListener);
+		matchEngineRegistryListener = null;
+		matchEngineFactoryRegistry = null;
 	}
 
 	/**
@@ -143,6 +164,16 @@ public class EMFCompareRCPPlugin extends Plugin {
 	}
 
 	/**
+	 * Returns the match engine factory registry to which extension will be registered.
+	 * 
+	 * @return the match engine factory registry to which extension will be registered
+	 * @since 3.0
+	 */
+	public IMatchEngine.Factory.Registry getMatchEngineFactoryRegistry() {
+		return matchEngineFactoryRegistry;
+	}
+
+	/**
 	 * Log the given message with the given severity to the logger of this plugin.
 	 * 
 	 * @param severity
diff --git a/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/extension/AbstractRegistryEventListener.java b/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/extension/AbstractRegistryEventListener.java
index 372b30fec..e85c75a50 100644
--- a/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/extension/AbstractRegistryEventListener.java
+++ b/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/extension/AbstractRegistryEventListener.java
@@ -1,266 +1,264 @@
-/*******************************************************************************

- * Copyright (c) 2012, 2013 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- * 

- * Contributors:

- *     Obeo - initial API and implementation

- *******************************************************************************/

-package org.eclipse.emf.compare.rcp.extension;

-

-import org.eclipse.core.runtime.IConfigurationElement;

-import org.eclipse.core.runtime.IExtension;

-import org.eclipse.core.runtime.IExtensionPoint;

-import org.eclipse.core.runtime.IExtensionRegistry;

-import org.eclipse.core.runtime.ILog;

-import org.eclipse.core.runtime.IRegistryEventListener;

-import org.eclipse.core.runtime.IStatus;

-import org.eclipse.core.runtime.Status;

-

-/**

- * Abstract utility class to listen to the {@link IExtensionRegistry}. It provides base implementation to

- * {@link #added(IExtension[])} and {@link #removed(IExtension[])}. Users must implement

- * {@link #readElement(IConfigurationElement, Action)} according to their extension schema.

- * <p>

- * The helper method {@link #readRegistry()} is browsing already registered extension to the extension

- * registry making it easy to read the registry after having added the listener to it.

- * <p>

- * {@link #readRegistry()} is delegating to {@link #readElement(IConfigurationElement, Action)}.

- * 

- * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>

- */

-public abstract class AbstractRegistryEventListener implements IRegistryEventListener {

-

-	/**

-	 * Enumeration that says if the {@link IConfigurationElement} is to be added or removed from the

-	 * {@link IExtensionRegistry}.

-	 * 

-	 * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>

-	 */

-	protected static enum Action {

-		/**

-		 * The {@link IConfigurationElement} is to be added.

-		 */

-		ADD,

-		/**

-		 * The {@link IConfigurationElement} is to be removed.

-		 */

-		REMOVE

-	}

-

-	/**

-	 * The namespace of the extension point to be monitored.

-	 */

-	private final String namespace;

-

-	/**

-	 * The extension point ID to be monitored.

-	 */

-	private final String extensionPointID;

-

-	private final ILog log;

-

-	/**

-	 * Creates a new registry event listener.

-	 * 

-	 * @param namespace

-	 *            The namespace of the extension point to be monitored.

-	 * @param extensionPointID

-	 *            The extension point ID to be monitored

-	 * @param log

-	 *            The log object to be used to log error and/or warning.

-	 */

-	public AbstractRegistryEventListener(String namespace, String extensionPointID, ILog log) {

-		this.namespace = namespace;

-		this.extensionPointID = extensionPointID;

-		this.log = log;

-	}

-

-	/**

-	 * Reads the given registry and call {@link #readElement(IConfigurationElement, Action)} as the read

-	 * {@link IConfigurationElement} were just added to it.

-	 * 

-	 * @param extensionRegistry

-	 *            the registry to read.

-	 */

-	public void readRegistry(IExtensionRegistry extensionRegistry) {

-		IExtensionPoint point = extensionRegistry.getExtensionPoint(namespace, extensionPointID);

-		if (point != null) {

-			IConfigurationElement[] elements = point.getConfigurationElements();

-			for (int i = 0; i < elements.length; i++) {

-				internalReadElement(elements[i], Action.ADD);

-			}

-		}

-	}

-

-	/**

-	 * Reads the given {@code element}. This method can be call when the element is added or remove. The

-	 * {@code action} reflect it. It returns true if the element is recognized as valid regarding the

-	 * monitored extension point. It will be call on sub elements recursively for all recognized ones.

-	 * 

-	 * @param element

-	 *            the element to be read.

-	 * @param action

-	 *            is the element added or removed.

-	 * @return true if the element is recognized as valid regarding the monitored extension point.

-	 */

-	protected boolean readElement(IConfigurationElement element, Action action) {

-		final boolean ret;

-		if (validateExtensionElement(element)) {

-			switch (action) {

-				case ADD:

-					ret = addedValid(element);

-					break;

-				case REMOVE:

-					ret = removedValid(element);

-					break;

-				default:

-					ret = false;

-					break;

-			}

-		} else {

-			ret = false;

-		}

-		return ret;

-	}

-

-	/**

-	 * Validates if the given element is an element for the given extension and is well constructed. Returns

-	 * true if the element should be further parsed for addition or removal.

-	 * 

-	 * @param element

-	 *            the element to validate.

-	 * @return true if the element should be further parsed for addition or removal, else otherwise.

-	 */

-	protected abstract boolean validateExtensionElement(IConfigurationElement element);

-

-	/**

-	 * Process the given element as the addition of a valid element extension.

-	 * 

-	 * @param element

-	 *            the element to be added.

-	 * @return true if the given element has been added and if its children should be processed, false

-	 *         otherwise.

-	 */

-	protected abstract boolean addedValid(IConfigurationElement element);

-

-	/**

-	 * Process the given element as the removal of a valid element extension.

-	 * 

-	 * @param element

-	 *            the element to be removed.

-	 * @return true if the given element has been removed and if its children should be processed, false

-	 *         otherwise.

-	 */

-	protected abstract boolean removedValid(IConfigurationElement element);

-

-	/**

-	 * Reads the given element and, if recognized, browse recursively the children and try to read it.

-	 * 

-	 * @param element

-	 *            the element to be read.

-	 * @param action

-	 *            is the element added or removed.

-	 */

-	private void internalReadElement(IConfigurationElement element, Action action) {

-		boolean recognized = readElement(element, action);

-		if (recognized) {

-			IConfigurationElement[] children = element.getChildren();

-			for (int i = 0; i < children.length; ++i) {

-				internalReadElement(children[i], action);

-			}

-		} else {

-			log(IStatus.ERROR, element, "Error processing extension: " + element);

-		}

-	}

-

-	/**

-	 * Delegates the logging of a missing attribute to {@link #log(IConfigurationElement, String)} with a

-	 * proper message.

-	 * 

-	 * @param element

-	 *            the element to which an attribute is missing.

-	 * @param attributeName

-	 *            the name of the missing attribute.

-	 */

-	protected void logMissingAttribute(IConfigurationElement element, String attributeName) {

-		log(IStatus.ERROR, element, "The required attribute '" + attributeName + "' not defined");

-	}

-

-	/**

-	 * Log the error to the current plugin logger.

-	 * 

-	 * @param element

-	 *            the element from which comes to the error.

-	 * @param message

-	 *            the message to be logged.

-	 */

-	protected void log(int severity, IConfigurationElement element, String message) {

-		log.log(new Status(severity, element.getDeclaringExtension().getContributor().getName(), message));

-	}

-

-	/**

-	 * Log the error to the current plugin logger.

-	 * 

-	 * @param element

-	 *            the element from which comes to the error.

-	 * @param message

-	 *            the message to be logged.

-	 */

-	protected void log(IConfigurationElement element, Throwable t) {

-		log.log(new Status(IStatus.ERROR, element.getDeclaringExtension().getContributor().getName(), t

-				.getMessage(), t));

-	}

-

-	/**

-	 * {@inheritDoc}

-	 * 

-	 * @see org.eclipse.core.runtime.IRegistryEventListener#added(org.eclipse.core.runtime.IExtension[])

-	 */

-	public void added(IExtension[] extensions) {

-		for (IExtension extension : extensions) {

-			if (extension.getExtensionPointUniqueIdentifier().equals(extensionPointID)) {

-				IConfigurationElement[] configurationElement = extension.getConfigurationElements();

-				for (int j = 0; j < configurationElement.length; ++j) {

-					internalReadElement(configurationElement[j], Action.ADD);

-				}

-			}

-		}

-	}

-

-	/**

-	 * {@inheritDoc}

-	 * 

-	 * @see org.eclipse.core.runtime.IRegistryEventListener#removed(org.eclipse.core.runtime.IExtension[])

-	 */

-	public void removed(IExtension[] extensions) {

-		for (IExtension extension : extensions) {

-			if (extension.getExtensionPointUniqueIdentifier().equals(extensionPointID)) {

-				IConfigurationElement[] configurationElement = extension.getConfigurationElements();

-				for (int j = 0; j < configurationElement.length; ++j) {

-					internalReadElement(configurationElement[j], Action.REMOVE);

-				}

-			}

-		}

-	}

-

-	/**

-	 * {@inheritDoc}

-	 * 

-	 * @see org.eclipse.core.runtime.IRegistryEventListener#added(org.eclipse.core.runtime.IExtensionPoint[])

-	 */

-	public void added(IExtensionPoint[] extensionPoints) {

-		// no need to listen to this.

-	}

-

-	/**

-	 * {@inheritDoc}

-	 * 

-	 * @see org.eclipse.core.runtime.IRegistryEventListener#removed(org.eclipse.core.runtime.IExtensionPoint[])

-	 */

-	public void removed(IExtensionPoint[] extensionPoints) {

-		// no need to listen to this.

-	}

-}

+/*******************************************************************************
+ * Copyright (c) 2012, 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.rcp.extension;
+
+import org.eclipse.core.runtime.IConfigurationElement;
+import org.eclipse.core.runtime.IExtension;
+import org.eclipse.core.runtime.IExtensionPoint;
+import org.eclipse.core.runtime.IExtensionRegistry;
+import org.eclipse.core.runtime.ILog;
+import org.eclipse.core.runtime.IRegistryEventListener;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Status;
+
+/**
+ * Abstract utility class to listen to the {@link IExtensionRegistry}. It provides base implementation to
+ * {@link #added(IExtension[])} and {@link #removed(IExtension[])}. Users must implement
+ * {@link #readElement(IConfigurationElement, Action)} according to their extension schema.
+ * <p>
+ * The helper method {@link #readRegistry()} is browsing already registered extension to the extension
+ * registry making it easy to read the registry after having added the listener to it.
+ * <p>
+ * {@link #readRegistry()} is delegating to {@link #readElement(IConfigurationElement, Action)}.
+ * 
+ * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>
+ */
+public abstract class AbstractRegistryEventListener implements IRegistryEventListener {
+
+	/**
+	 * Enumeration that says if the {@link IConfigurationElement} is to be added or removed from the
+	 * {@link IExtensionRegistry}.
+	 * 
+	 * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>
+	 */
+	protected static enum Action {
+		/**
+		 * The {@link IConfigurationElement} is to be added.
+		 */
+		ADD,
+		/**
+		 * The {@link IConfigurationElement} is to be removed.
+		 */
+		REMOVE
+	}
+
+	/**
+	 * The namespace of the extension point to be monitored.
+	 */
+	private final String namespace;
+
+	/**
+	 * The extension point ID to be monitored.
+	 */
+	private final String extensionPointID;
+
+	private final ILog log;
+
+	/**
+	 * Creates a new registry event listener.
+	 * 
+	 * @param namespace
+	 *            The namespace of the extension point to be monitored.
+	 * @param extensionPointID
+	 *            The extension point ID to be monitored
+	 * @param log
+	 *            The log object to be used to log error and/or warning.
+	 */
+	public AbstractRegistryEventListener(String namespace, String extensionPointID, ILog log) {
+		this.namespace = namespace;
+		this.extensionPointID = extensionPointID;
+		this.log = log;
+	}
+
+	/**
+	 * Reads the given registry and call {@link #readElement(IConfigurationElement, Action)} as the read
+	 * {@link IConfigurationElement} were just added to it.
+	 * 
+	 * @param extensionRegistry
+	 *            the registry to read.
+	 */
+	public void readRegistry(IExtensionRegistry extensionRegistry) {
+		IExtensionPoint point = extensionRegistry.getExtensionPoint(namespace, extensionPointID);
+		if (point != null) {
+			IConfigurationElement[] elements = point.getConfigurationElements();
+			for (int i = 0; i < elements.length; i++) {
+				internalReadElement(elements[i], Action.ADD);
+			}
+		}
+	}
+
+	/**
+	 * Reads the given {@code element}. This method can be call when the element is added or remove. The
+	 * {@code action} reflect it. It returns true if the element is recognized as valid regarding the
+	 * monitored extension point. It will be call on sub elements recursively for all recognized ones.
+	 * 
+	 * @param element
+	 *            the element to be read.
+	 * @param action
+	 *            is the element added or removed.
+	 * @return true if the element is recognized as valid regarding the monitored extension point.
+	 */
+	protected boolean readElement(IConfigurationElement element, Action action) {
+		final boolean ret;
+		if (validateExtensionElement(element)) {
+			switch (action) {
+				case ADD:
+					ret = addedValid(element);
+					break;
+				case REMOVE:
+					ret = removedValid(element);
+					break;
+				default:
+					ret = false;
+					break;
+			}
+		} else {
+			ret = false;
+		}
+		return ret;
+	}
+
+	/**
+	 * Validates if the given element is an element for the given extension and is well constructed. Returns
+	 * true if the element should be further parsed for addition or removal.
+	 * 
+	 * @param element
+	 *            the element to validate.
+	 * @return true if the element should be further parsed for addition or removal, else otherwise.
+	 */
+	protected abstract boolean validateExtensionElement(IConfigurationElement element);
+
+	/**
+	 * Process the given element as the addition of a valid element extension.
+	 * 
+	 * @param element
+	 *            the element to be added.
+	 * @return true if the given element has been added and if its children should be processed, false
+	 *         otherwise.
+	 */
+	protected abstract boolean addedValid(IConfigurationElement element);
+
+	/**
+	 * Process the given element as the removal of a valid element extension.
+	 * 
+	 * @param element
+	 *            the element to be removed.
+	 * @return true if the given element has been removed and if its children should be processed, false
+	 *         otherwise.
+	 */
+	protected abstract boolean removedValid(IConfigurationElement element);
+
+	/**
+	 * Reads the given element and, if recognized, browse recursively the children and try to read it.
+	 * 
+	 * @param element
+	 *            the element to be read.
+	 * @param action
+	 *            is the element added or removed.
+	 */
+	private void internalReadElement(IConfigurationElement element, Action action) {
+		boolean recognized = readElement(element, action);
+		if (recognized) {
+			IConfigurationElement[] children = element.getChildren();
+			for (int i = 0; i < children.length; ++i) {
+				internalReadElement(children[i], action);
+			}
+		}
+	}
+
+	/**
+	 * Delegates the logging of a missing attribute to {@link #log(IConfigurationElement, String)} with a
+	 * proper message.
+	 * 
+	 * @param element
+	 *            the element to which an attribute is missing.
+	 * @param attributeName
+	 *            the name of the missing attribute.
+	 */
+	protected void logMissingAttribute(IConfigurationElement element, String attributeName) {
+		log(IStatus.ERROR, element, "The required attribute '" + attributeName + "' not defined");
+	}
+
+	/**
+	 * Log the error to the current plugin logger.
+	 * 
+	 * @param element
+	 *            the element from which comes to the error.
+	 * @param message
+	 *            the message to be logged.
+	 */
+	protected void log(int severity, IConfigurationElement element, String message) {
+		log.log(new Status(severity, element.getDeclaringExtension().getContributor().getName(), message));
+	}
+
+	/**
+	 * Log the error to the current plugin logger.
+	 * 
+	 * @param element
+	 *            the element from which comes to the error.
+	 * @param message
+	 *            the message to be logged.
+	 */
+	protected void log(IConfigurationElement element, Throwable t) {
+		log.log(new Status(IStatus.ERROR, element.getDeclaringExtension().getContributor().getName(), t
+				.getMessage(), t));
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.core.runtime.IRegistryEventListener#added(org.eclipse.core.runtime.IExtension[])
+	 */
+	public void added(IExtension[] extensions) {
+		for (IExtension extension : extensions) {
+			if (extension.getExtensionPointUniqueIdentifier().equals(extensionPointID)) {
+				IConfigurationElement[] configurationElement = extension.getConfigurationElements();
+				for (int j = 0; j < configurationElement.length; ++j) {
+					internalReadElement(configurationElement[j], Action.ADD);
+				}
+			}
+		}
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.core.runtime.IRegistryEventListener#removed(org.eclipse.core.runtime.IExtension[])
+	 */
+	public void removed(IExtension[] extensions) {
+		for (IExtension extension : extensions) {
+			if (extension.getExtensionPointUniqueIdentifier().equals(extensionPointID)) {
+				IConfigurationElement[] configurationElement = extension.getConfigurationElements();
+				for (int j = 0; j < configurationElement.length; ++j) {
+					internalReadElement(configurationElement[j], Action.REMOVE);
+				}
+			}
+		}
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.core.runtime.IRegistryEventListener#added(org.eclipse.core.runtime.IExtensionPoint[])
+	 */
+	public void added(IExtensionPoint[] extensionPoints) {
+		// no need to listen to this.
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.core.runtime.IRegistryEventListener#removed(org.eclipse.core.runtime.IExtensionPoint[])
+	 */
+	public void removed(IExtensionPoint[] extensionPoints) {
+		// no need to listen to this.
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/internal/match/MatchEngineFactoryRegistryListener.java b/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/internal/match/MatchEngineFactoryRegistryListener.java
new file mode 100644
index 000000000..8169c3329
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.rcp/src/org/eclipse/emf/compare/rcp/internal/match/MatchEngineFactoryRegistryListener.java
@@ -0,0 +1,126 @@
+/*******************************************************************************
+ * Copyright (c) 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.rcp.internal.match;
+
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IConfigurationElement;
+import org.eclipse.core.runtime.ILog;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.rcp.extension.AbstractRegistryEventListener;
+import org.eclipse.emf.compare.rcp.internal.EMFCompareRCPMessages;
+
+/**
+ * Listener for contributions to the match engine extension.
+ * 
+ * @author <a href="mailto:axel.richard@obeo.fr">Axel Richard</a>
+ */
+public class MatchEngineFactoryRegistryListener extends AbstractRegistryEventListener {
+
+	/** TAG_ENGINE. */
+	private static final String TAG_ENGINE_FACTORY = "engineFactory"; //$NON-NLS-1$
+
+	/** ATT_CLASS. */
+	private static final String ATT_CLASS = "class"; //$NON-NLS-1$
+
+	/** ATT_RANKING. */
+	private static final String ATT_RANKING = "ranking"; //$NON-NLS-1$
+
+	/** The match engine factory registry to which extension will be registered. */
+	private final IMatchEngine.Factory.Registry matchEngineFactoryRegistry;
+
+	/**
+	 * Creates a new registry listener with the given match engine factory registry to which extension will be
+	 * registered.
+	 * 
+	 * @param registry
+	 *            the match engine factory registry to which extension will be registered.
+	 * @param pluginID
+	 *            The pluginID of the extension point to be monitored.
+	 * @param extensionPointID
+	 *            The extension point ID to be monitored.
+	 * @param log
+	 *            The log object to be used to log error and/or warning.
+	 */
+	public MatchEngineFactoryRegistryListener(String pluginID, String extensionPointID, ILog log,
+			IMatchEngine.Factory.Registry registry) {
+		super(pluginID, extensionPointID, log);
+		this.matchEngineFactoryRegistry = registry;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.rcp.extension.AbstractRegistryEventListener#validateExtensionElement(org.eclipse.core.runtime.IConfigurationElement)
+	 */
+	@Override
+	protected boolean validateExtensionElement(IConfigurationElement element) {
+		final boolean ret;
+		if (TAG_ENGINE_FACTORY.equals(element.getName())) {
+			if (element.getAttribute(ATT_CLASS) == null) {
+				logMissingAttribute(element, ATT_CLASS);
+				ret = false;
+			} else if (element.getAttribute(ATT_RANKING) == null) {
+				logMissingAttribute(element, ATT_RANKING);
+				ret = false;
+			} else if (element.getAttribute(ATT_RANKING) != null) {
+				String rankingStr = element.getAttribute(ATT_RANKING);
+				try {
+					Integer.parseInt(rankingStr);
+				} catch (NumberFormatException nfe) {
+					log(IStatus.ERROR, element, EMFCompareRCPMessages.getString(
+							"malformed.extension.attribute", //$NON-NLS-1$
+							ATT_RANKING));
+					return false;
+				}
+				ret = true;
+			} else {
+				ret = true;
+			}
+		} else {
+			ret = false;
+		}
+		return ret;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.rcp.extension.AbstractRegistryEventListener#addedValid(org.eclipse.core.runtime.IConfigurationElement)
+	 */
+	@Override
+	protected boolean addedValid(IConfigurationElement element) {
+		try {
+			IMatchEngine.Factory matchEngineFactory = (IMatchEngine.Factory)element
+					.createExecutableExtension(ATT_CLASS);
+			matchEngineFactory.setRanking(Integer.parseInt(element.getAttribute(ATT_RANKING)));
+			IMatchEngine.Factory previous = matchEngineFactoryRegistry.add(matchEngineFactory);
+			if (previous != null) {
+				log(IStatus.WARNING, element, EMFCompareRCPMessages.getString(
+						"duplicate.extension", matchEngineFactoryRegistry.getClass().getName())); //$NON-NLS-1$
+			}
+		} catch (CoreException e) {
+			log(IStatus.ERROR, element, e.getMessage());
+		}
+		return true;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.rcp.extension.AbstractRegistryEventListener#removedValid(org.eclipse.core.runtime.IConfigurationElement)
+	 */
+	@Override
+	protected boolean removedValid(IConfigurationElement element) {
+		matchEngineFactoryRegistry.remove(element.getAttribute(ATT_CLASS));
+		return true;
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/fullcomparison/ProximityComparisonTest.java b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/fullcomparison/ProximityComparisonTest.java
index e354bbec3..2a46ec7e1 100644
--- a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/fullcomparison/ProximityComparisonTest.java
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/fullcomparison/ProximityComparisonTest.java
@@ -1,210 +1,228 @@
-/**

- * Copyright (c) 2012 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- * 

- * Contributors:

- *     Obeo - initial API and implementation

- */

-package org.eclipse.emf.compare.tests.fullcomparison;

-

-import static junit.framework.Assert.assertTrue;

-import static org.junit.Assert.assertEquals;

-import static org.junit.Assert.assertFalse;

-import static org.junit.Assert.fail;

-

-import com.google.common.collect.Iterators;

-import com.google.common.collect.Lists;

-

-import java.io.ByteArrayOutputStream;

-import java.io.PrintStream;

-import java.util.Iterator;

-import java.util.List;

-

-import org.eclipse.emf.compare.AttributeChange;

-import org.eclipse.emf.compare.Comparison;

-import org.eclipse.emf.compare.Diff;

-import org.eclipse.emf.compare.DifferenceKind;

-import org.eclipse.emf.compare.DifferenceSource;

-import org.eclipse.emf.compare.EMFCompare;

-import org.eclipse.emf.compare.Match;

-import org.eclipse.emf.compare.ReferenceChange;

-import org.eclipse.emf.compare.ResourceAttachmentChange;

-import org.eclipse.emf.compare.match.DefaultMatchEngine;

-import org.eclipse.emf.compare.scope.IComparisonScope;

-import org.eclipse.emf.compare.tests.framework.EMFCompareAssert;

-import org.eclipse.emf.compare.tests.framework.EMFCompareTestBase;

-import org.eclipse.emf.compare.tests.fullcomparison.data.distance.DistanceMatchInputData;

-import org.eclipse.emf.compare.tests.suite.AllTests;

-import org.eclipse.emf.compare.utils.EMFComparePrettyPrinter;

-import org.eclipse.emf.compare.utils.UseIdentifiers;

-import org.eclipse.emf.ecore.EObject;

-import org.eclipse.emf.ecore.EPackage;

-import org.eclipse.emf.ecore.EcorePackage;

-import org.eclipse.emf.ecore.resource.Resource;

-import org.eclipse.emf.ecore.util.EcoreUtil;

-import org.junit.Before;

-import org.junit.Test;

-

-@SuppressWarnings("nls")

-public class ProximityComparisonTest extends EMFCompareTestBase {

-	@Before

-	public void setUp() throws Exception {

-		AllTests.fillEMFRegistries();

-	}

-

-	private DistanceMatchInputData inputData = new DistanceMatchInputData();

-

-	@Test

-	public void singleEObjectTest() throws Exception {

-		EPackage v1 = EcoreUtil.copy(EcorePackage.eINSTANCE);

-		EPackage v2 = EcoreUtil.copy(EcorePackage.eINSTANCE);

-		v1.getEClassifiers().clear();

-		v2.getEClassifiers().clear();

-

-		final IComparisonScope scope = EMFCompare.createDefaultScope(v1, v2);

-		Comparison result = EMFCompare.builder().build().compare(scope);

-		assertAllMatched(Lists.newArrayList(v1), result);

-		assertEquals("We are supposed to have zero diffs", 0, result.getDifferences().size());

-	}

-

-	@Test

-	public void matchingSmallRenameChanges() throws Exception {

-		Resource left = inputData.getCompareLeft();

-		Resource right = inputData.getCompareRight();

-		final IComparisonScope scope = EMFCompare.createDefaultScope(left, right);

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		assertEquals("We are supposed to have one rename diff", 1, result.getDifferences().size());

-	}

-

-	@Test

-	public void matchingIndenticInstances() throws Exception {

-

-		EPackage v1 = EcoreUtil.copy(EcorePackage.eINSTANCE);

-		EPackage v2 = EcoreUtil.copy(EcorePackage.eINSTANCE);

-

-		final IComparisonScope scope = EMFCompare.createDefaultScope(v1, v2);

-		Comparison result = EMFCompare.builder().build().compare(scope);

-

-		assertAllMatched(Lists.newArrayList(v1), result);

-		assertEquals("We are supposed to have zero diffs", 0, result.getDifferences().size());

-	}

-

-	@Test

-	public void smallChangeOnEPackage() throws Exception {

-

-		EPackage v1 = EcoreUtil.copy(EcorePackage.eINSTANCE);

-		EPackage v2 = EcoreUtil.copy(EcorePackage.eINSTANCE);

-		v2.setName("renamed");

-

-		final IComparisonScope scope = EMFCompare.createDefaultScope(v1, v2);

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		assertAllMatched(Lists.newArrayList(v1), result);

-		assertEquals("We are supposed to have a rename", 1, result.getDifferences().size());

-	}

-

-	@Test

-	public void packageAddDelete() throws Exception {

-		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.getPackageAddDeleteLeft(),

-				inputData.getPackageAddDeleteRight());

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		EMFComparePrettyPrinter.printComparison(result, System.out);

-		final List<Diff> differences = result.getDifferences();

-		EMFCompareAssert.assertAddedToReference(differences, "p1.p2", "eSubpackages", "p1.p2.subPackage",

-				DifferenceSource.LEFT);

-		EMFCompareAssert.assertRemovedFromReference(differences, "p1", "eSubpackages", "p1.another",

-				DifferenceSource.LEFT);

-		assertEquals("We are supposed to have zero diffs", 2, result.getDifferences().size());

-	}

-

-	@Test

-	public void packageAddRemoveNoRename() throws Exception {

-		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData

-				.getPackageAddRemoveNoRenameLeft(), inputData.getPackageAddRemoveNoRenameRight());

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		EMFComparePrettyPrinter.printComparison(result, System.out);

-		final List<Diff> differences = result.getDifferences();

-		// EMFCompareAssert.assertAddedToReference(differences, "p1.p2", "eSubpackages", "p1.p2.subPackage",

-		// DifferenceSource.LEFT);

-		// EMFCompareAssert.assertRemovedFromReference(differences, "p1", "eSubpackages", "p1.another",

-		// DifferenceSource.LEFT);

-		assertEquals("We are supposed to have zero diffs", 2, result.getDifferences().size());

-	}

-

-	@Test

-	public void alwaysTakeTheClosestNoMatterTheIterationOrder() throws Exception {

-		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.getVerySmallLeft(), inputData

-				.getVerySmallRight());

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		assertEquals(

-				"The Match took on element which is close enough (in the limits) preventing the next iteration to take it (it was closest)",

-				1, result.getDifferences().size());

-

-	}

-

-	@Test

-	public void addRemoveAndNotRename() throws Exception {

-		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.get391657Left(), inputData

-				.get391657Right());

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		Iterator<AttributeChange> attrChanges = Iterators.filter(result.getDifferences().iterator(),

-				AttributeChange.class);

-		assertFalse("We are supposed to detect an addition/remove (and not a rename if that's what we get)",

-				attrChanges.hasNext());

-

-	}

-

-	@Test

-	public void resourceRootChange() throws Exception {

-		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.get390666Left(), inputData

-				.get390666Right(), inputData.get390666Ancestor());

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		Iterator<ResourceAttachmentChange> attrChanges = Iterators.filter(result.getDifferences().iterator(),

-				ResourceAttachmentChange.class);

-		assertTrue("We are supposed to detect a new attachment to a resource", attrChanges.hasNext());

-

-	}

-

-	@Test

-	public void moveInAReferenceShouldNotAffectMatch() throws Exception {

-		/*

-		 * See bug #391798 : moving elements a lot in a reference (like in changing index) should not affect

-		 * the matching very much.

-		 */

-		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.get391798Left(), inputData

-				.get391798Right());

-		Comparison result = EMFCompare.builder().setMatchEngine(

-				DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(scope);

-		for (Diff dif : result.getDifferences()) {

-			if (dif instanceof ReferenceChange && dif.getKind() == DifferenceKind.MOVE) {

-

-			} else {

-				fail("We should only detect moves in the reference.");

-			}

-		}

-

-	}

-

-	private String print(Comparison result) {

-		ByteArrayOutputStream baos = new ByteArrayOutputStream();

-		PrintStream ps = new PrintStream(baos);

-		EMFComparePrettyPrinter.printDifferences(result, ps);

-		return baos.toString();

-	}

-

-	private void assertAllMatched(Iterable<? extends EObject> eObjects, Comparison comparison) {

-		for (EObject eObject : eObjects) {

-			final Match match = comparison.getMatch(eObject);

-			assertTrue(eObject + " has no match", match != null);

-		}

-	}

-}

+/**
+ * Copyright (c) 2012 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ */
+package org.eclipse.emf.compare.tests.fullcomparison;
+
+import static junit.framework.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.fail;
+
+import com.google.common.collect.Iterators;
+import com.google.common.collect.Lists;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.Iterator;
+import java.util.List;
+
+import org.eclipse.emf.compare.AttributeChange;
+import org.eclipse.emf.compare.Comparison;
+import org.eclipse.emf.compare.Diff;
+import org.eclipse.emf.compare.DifferenceKind;
+import org.eclipse.emf.compare.DifferenceSource;
+import org.eclipse.emf.compare.EMFCompare;
+import org.eclipse.emf.compare.Match;
+import org.eclipse.emf.compare.ReferenceChange;
+import org.eclipse.emf.compare.ResourceAttachmentChange;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryImpl;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryRegistryImpl;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+import org.eclipse.emf.compare.tests.framework.EMFCompareAssert;
+import org.eclipse.emf.compare.tests.framework.EMFCompareTestBase;
+import org.eclipse.emf.compare.tests.fullcomparison.data.distance.DistanceMatchInputData;
+import org.eclipse.emf.compare.tests.suite.AllTests;
+import org.eclipse.emf.compare.utils.EMFComparePrettyPrinter;
+import org.eclipse.emf.compare.utils.UseIdentifiers;
+import org.eclipse.emf.ecore.EObject;
+import org.eclipse.emf.ecore.EPackage;
+import org.eclipse.emf.ecore.EcorePackage;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.util.EcoreUtil;
+import org.junit.Before;
+import org.junit.Test;
+
+@SuppressWarnings("nls")
+public class ProximityComparisonTest extends EMFCompareTestBase {
+	@Before
+	public void setUp() throws Exception {
+		AllTests.fillEMFRegistries();
+	}
+
+	private DistanceMatchInputData inputData = new DistanceMatchInputData();
+
+	@Test
+	public void singleEObjectTest() throws Exception {
+		EPackage v1 = EcoreUtil.copy(EcorePackage.eINSTANCE);
+		EPackage v2 = EcoreUtil.copy(EcorePackage.eINSTANCE);
+		v1.getEClassifiers().clear();
+		v2.getEClassifiers().clear();
+
+		final IComparisonScope scope = EMFCompare.createDefaultScope(v1, v2);
+		Comparison result = EMFCompare.builder().build().compare(scope);
+		assertAllMatched(Lists.newArrayList(v1), result);
+		assertEquals("We are supposed to have zero diffs", 0, result.getDifferences().size());
+	}
+
+	@Test
+	public void matchingSmallRenameChanges() throws Exception {
+		Resource left = inputData.getCompareLeft();
+		Resource right = inputData.getCompareRight();
+		final IComparisonScope scope = EMFCompare.createDefaultScope(left, right);
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		assertEquals("We are supposed to have one rename diff", 1, result.getDifferences().size());
+	}
+
+	@Test
+	public void matchingIndenticInstances() throws Exception {
+
+		EPackage v1 = EcoreUtil.copy(EcorePackage.eINSTANCE);
+		EPackage v2 = EcoreUtil.copy(EcorePackage.eINSTANCE);
+
+		final IComparisonScope scope = EMFCompare.createDefaultScope(v1, v2);
+		Comparison result = EMFCompare.builder().build().compare(scope);
+
+		assertAllMatched(Lists.newArrayList(v1), result);
+		assertEquals("We are supposed to have zero diffs", 0, result.getDifferences().size());
+	}
+
+	@Test
+	public void smallChangeOnEPackage() throws Exception {
+
+		EPackage v1 = EcoreUtil.copy(EcorePackage.eINSTANCE);
+		EPackage v2 = EcoreUtil.copy(EcorePackage.eINSTANCE);
+		v2.setName("renamed");
+
+		final IComparisonScope scope = EMFCompare.createDefaultScope(v1, v2);
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		assertAllMatched(Lists.newArrayList(v1), result);
+		assertEquals("We are supposed to have a rename", 1, result.getDifferences().size());
+	}
+
+	@Test
+	public void packageAddDelete() throws Exception {
+		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.getPackageAddDeleteLeft(),
+				inputData.getPackageAddDeleteRight());
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		EMFComparePrettyPrinter.printComparison(result, System.out);
+		final List<Diff> differences = result.getDifferences();
+		EMFCompareAssert.assertAddedToReference(differences, "p1.p2", "eSubpackages", "p1.p2.subPackage",
+				DifferenceSource.LEFT);
+		EMFCompareAssert.assertRemovedFromReference(differences, "p1", "eSubpackages", "p1.another",
+				DifferenceSource.LEFT);
+		assertEquals("We are supposed to have zero diffs", 2, result.getDifferences().size());
+	}
+
+	@Test
+	public void packageAddRemoveNoRename() throws Exception {
+		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData
+				.getPackageAddRemoveNoRenameLeft(), inputData.getPackageAddRemoveNoRenameRight());
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		EMFComparePrettyPrinter.printComparison(result, System.out);
+		final List<Diff> differences = result.getDifferences();
+		// EMFCompareAssert.assertAddedToReference(differences, "p1.p2", "eSubpackages", "p1.p2.subPackage",
+		// DifferenceSource.LEFT);
+		// EMFCompareAssert.assertRemovedFromReference(differences, "p1", "eSubpackages", "p1.another",
+		// DifferenceSource.LEFT);
+		assertEquals("We are supposed to have zero diffs", 2, result.getDifferences().size());
+	}
+
+	@Test
+	public void alwaysTakeTheClosestNoMatterTheIterationOrder() throws Exception {
+		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.getVerySmallLeft(), inputData
+				.getVerySmallRight());
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		assertEquals(
+				"The Match took on element which is close enough (in the limits) preventing the next iteration to take it (it was closest)",
+				1, result.getDifferences().size());
+
+	}
+
+	@Test
+	public void addRemoveAndNotRename() throws Exception {
+		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.get391657Left(), inputData
+				.get391657Right());
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		Iterator<AttributeChange> attrChanges = Iterators.filter(result.getDifferences().iterator(),
+				AttributeChange.class);
+		assertFalse("We are supposed to detect an addition/remove (and not a rename if that's what we get)",
+				attrChanges.hasNext());
+
+	}
+
+	@Test
+	public void resourceRootChange() throws Exception {
+		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.get390666Left(), inputData
+				.get390666Right(), inputData.get390666Ancestor());
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		Iterator<ResourceAttachmentChange> attrChanges = Iterators.filter(result.getDifferences().iterator(),
+				ResourceAttachmentChange.class);
+		assertTrue("We are supposed to detect a new attachment to a resource", attrChanges.hasNext());
+
+	}
+
+	@Test
+	public void moveInAReferenceShouldNotAffectMatch() throws Exception {
+		/*
+		 * See bug #391798 : moving elements a lot in a reference (like in changing index) should not affect
+		 * the matching very much.
+		 */
+		final IComparisonScope scope = EMFCompare.createDefaultScope(inputData.get391798Left(), inputData
+				.get391798Right());
+		IMatchEngine.Factory.Registry matchEngineFactoryRegistry = new MatchEngineFactoryRegistryImpl();
+		matchEngineFactoryRegistry.add(new MatchEngineFactoryImpl(UseIdentifiers.NEVER));
+		Comparison result = EMFCompare.builder().setMatchEngineFactoryRegistry(matchEngineFactoryRegistry)
+				.build().compare(scope);
+		for (Diff dif : result.getDifferences()) {
+			if (dif instanceof ReferenceChange && dif.getKind() == DifferenceKind.MOVE) {
+
+			} else {
+				fail("We should only detect moves in the reference.");
+			}
+		}
+
+	}
+
+	private String print(Comparison result) {
+		ByteArrayOutputStream baos = new ByteArrayOutputStream();
+		PrintStream ps = new PrintStream(baos);
+		EMFComparePrettyPrinter.printDifferences(result, ps);
+		return baos.toString();
+	}
+
+	private void assertAllMatched(Iterable<? extends EObject> eObjects, Comparison comparison) {
+		for (EObject eObject : eObjects) {
+			final Match match = comparison.getMatch(eObject);
+			assertTrue(eObject + " has no match", match != null);
+		}
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/match/MatchEngineFactoryRegistryTest.java b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/match/MatchEngineFactoryRegistryTest.java
new file mode 100644
index 000000000..1f829e966
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/match/MatchEngineFactoryRegistryTest.java
@@ -0,0 +1,85 @@
+/*******************************************************************************
+ * Copyright (c) 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.tests.match;
+
+import static junit.framework.Assert.assertEquals;
+import static junit.framework.Assert.assertFalse;
+import static junit.framework.Assert.assertTrue;
+
+import java.io.IOException;
+
+import org.eclipse.emf.compare.EMFCompare;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryImpl;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryRegistryImpl;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+import org.eclipse.emf.compare.tests.fullcomparison.data.identifier.IdentifierMatchInputData;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.junit.Test;
+
+public class MatchEngineFactoryRegistryTest {
+
+	private IdentifierMatchInputData input = new IdentifierMatchInputData();
+
+	@Test
+	public void tesMatchEngineFactoryRegistry() throws IOException {
+		final Resource left = input.getExtlibraryLeft();
+		final Resource right = input.getExtlibraryRight();
+
+		final IMatchEngine.Factory.Registry registry = MatchEngineFactoryRegistryImpl
+				.createStandaloneInstance();
+
+		// Get the appropriate MatchEngineFactory.
+		final IComparisonScope scope = EMFCompare.createDefaultScope(left, right);
+		IMatchEngine.Factory factory = registry.getHighestRankingMatchEngineFactory(scope);
+
+		assertTrue(factory instanceof MatchEngineFactoryImpl);
+		assertEquals(1, registry.getMatchEngineFactories(scope).size());
+
+		// Add new MatchEngineFactory with higher ranking, but not appropriate
+		IMatchEngine.Factory factoryWithHighestRanking = new MatchEngineFactoryTest();
+		factoryWithHighestRanking.setRanking(100);
+		registry.add(factoryWithHighestRanking);
+
+		// Get the appropriate MatchEngineFactory.
+		factory = registry.getHighestRankingMatchEngineFactory(scope);
+
+		assertFalse(factory instanceof MatchEngineFactoryTest);
+		assertEquals(1, registry.getMatchEngineFactories(scope).size());
+
+		// Add new MatchEngineFactory with higher ranking
+		IMatchEngine.Factory factoryWithMiddleRanking = new MatchEngineFactoryOtherTest();
+		factoryWithMiddleRanking.setRanking(50);
+		registry.add(factoryWithMiddleRanking);
+
+		// Get the appropriate MatchEngineFactory.
+		factory = registry.getHighestRankingMatchEngineFactory(scope);
+
+		assertTrue(factory instanceof MatchEngineFactoryOtherTest);
+		assertEquals(2, registry.getMatchEngineFactories(scope).size());
+	}
+
+	private class MatchEngineFactoryTest extends MatchEngineFactoryImpl {
+
+		@Override
+		public boolean isMatchEngineFactoryFor(IComparisonScope scope) {
+			return false;
+		}
+	}
+
+	private class MatchEngineFactoryOtherTest extends MatchEngineFactoryImpl {
+
+		@Override
+		public boolean isMatchEngineFactoryFor(IComparisonScope scope) {
+			return true;
+		}
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/suite/AllTests.java b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/suite/AllTests.java
index 6722ab275..c9377fa13 100644
--- a/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/suite/AllTests.java
+++ b/plugins/org.eclipse.emf.compare.tests/src/org/eclipse/emf/compare/tests/suite/AllTests.java
@@ -1,85 +1,87 @@
-/*******************************************************************************

- * Copyright (c) 2012 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- * 

- * Contributors:

- *     Obeo - initial API and implementation

- *******************************************************************************/

-package org.eclipse.emf.compare.tests.suite;

-

-import junit.framework.JUnit4TestAdapter;

-import junit.framework.Test;

-import junit.textui.TestRunner;

-

-import org.eclipse.emf.compare.ComparePackage;

-import org.eclipse.emf.compare.tests.command.CommandStackTestSuite;

-import org.eclipse.emf.compare.tests.conflict.ConflictDetectionTest;

-import org.eclipse.emf.compare.tests.diff.DiffUtilTest;

-import org.eclipse.emf.compare.tests.diff.LCSPerformanceTest;

-import org.eclipse.emf.compare.tests.diff.URIDistanceTest;

-import org.eclipse.emf.compare.tests.edit.AllEditTests;

-import org.eclipse.emf.compare.tests.equi.EquiComputingTest;

-import org.eclipse.emf.compare.tests.fragmentation.FragmentationTest;

-import org.eclipse.emf.compare.tests.fullcomparison.DynamicInstanceComparisonTest;

-import org.eclipse.emf.compare.tests.fullcomparison.ExtLibraryTest;

-import org.eclipse.emf.compare.tests.fullcomparison.IdentifierComparisonTest;

-import org.eclipse.emf.compare.tests.fullcomparison.ProximityComparisonTest;

-import org.eclipse.emf.compare.tests.merge.ExtensionMergeTest;

-import org.eclipse.emf.compare.tests.merge.IndividualMergeOutOfScopeValuesTest;

-import org.eclipse.emf.compare.tests.merge.IndividualMergeTest;

-import org.eclipse.emf.compare.tests.merge.MultipleMergeTest;

-import org.eclipse.emf.compare.tests.nodes.NodesPackage;

-import org.eclipse.emf.compare.tests.nodes.util.NodesResourceFactoryImpl;

-import org.eclipse.emf.compare.tests.postprocess.PostProcessorTest;

-import org.eclipse.emf.compare.tests.req.ReqComputingTest;

-import org.eclipse.emf.compare.tests.scope.DefaultComparisonScopeTest;

-import org.eclipse.emf.ecore.EPackage;

-import org.eclipse.emf.ecore.resource.Resource;

-import org.junit.BeforeClass;

-import org.junit.runner.RunWith;

-import org.junit.runners.Suite;

-import org.junit.runners.Suite.SuiteClasses;

-

-/**

- * This test suite allows us to launch all tests for EMF Compare at once.

- * 

- * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>

- */

-@RunWith(Suite.class)

-@SuiteClasses({CompareTestSuite.class, DefaultComparisonScopeTest.class, IdentifierComparisonTest.class,

-		ExtLibraryTest.class, ConflictDetectionTest.class, ReqComputingTest.class, EquiComputingTest.class,

-		DiffUtilTest.class, LCSPerformanceTest.class, MultipleMergeTest.class, PostProcessorTest.class,

-		IndividualMergeTest.class, ExtensionMergeTest.class, IndividualMergeOutOfScopeValuesTest.class,

-		ProximityComparisonTest.class, DynamicInstanceComparisonTest.class, URIDistanceTest.class,

-		FragmentationTest.class, AllEditTests.class, CommandStackTestSuite.class, })

-public class AllTests {

-	/**

-	 * Standalone launcher for all of compare's tests.

-	 * 

-	 * @generated

-	 */

-	public static void main(String[] args) {

-		TestRunner.run(suite());

-	}

-

-	/**

-	 * This will return a suite populated with all tests available through this class.

-	 * 

-	 * @generated

-	 */

-	public static Test suite() {

-		return new JUnit4TestAdapter(CompareTestSuite.class);

-	}

-

-	@BeforeClass

-	public static void fillEMFRegistries() {

-		EPackage.Registry.INSTANCE.put(ComparePackage.eNS_URI, ComparePackage.eINSTANCE);

-		EPackage.Registry.INSTANCE.put(NodesPackage.eNS_URI, NodesPackage.eINSTANCE);

-

-		Resource.Factory.Registry.INSTANCE.getExtensionToFactoryMap().put("nodes", //$NON-NLS-1$

-				new NodesResourceFactoryImpl());

-	}

-}

+/*******************************************************************************
+ * Copyright (c) 2012 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.tests.suite;
+
+import junit.framework.JUnit4TestAdapter;
+import junit.framework.Test;
+import junit.textui.TestRunner;
+
+import org.eclipse.emf.compare.ComparePackage;
+import org.eclipse.emf.compare.tests.command.CommandStackTestSuite;
+import org.eclipse.emf.compare.tests.conflict.ConflictDetectionTest;
+import org.eclipse.emf.compare.tests.diff.DiffUtilTest;
+import org.eclipse.emf.compare.tests.diff.LCSPerformanceTest;
+import org.eclipse.emf.compare.tests.diff.URIDistanceTest;
+import org.eclipse.emf.compare.tests.edit.AllEditTests;
+import org.eclipse.emf.compare.tests.equi.EquiComputingTest;
+import org.eclipse.emf.compare.tests.fragmentation.FragmentationTest;
+import org.eclipse.emf.compare.tests.fullcomparison.DynamicInstanceComparisonTest;
+import org.eclipse.emf.compare.tests.fullcomparison.ExtLibraryTest;
+import org.eclipse.emf.compare.tests.fullcomparison.IdentifierComparisonTest;
+import org.eclipse.emf.compare.tests.fullcomparison.ProximityComparisonTest;
+import org.eclipse.emf.compare.tests.match.MatchEngineFactoryRegistryTest;
+import org.eclipse.emf.compare.tests.merge.ExtensionMergeTest;
+import org.eclipse.emf.compare.tests.merge.IndividualMergeOutOfScopeValuesTest;
+import org.eclipse.emf.compare.tests.merge.IndividualMergeTest;
+import org.eclipse.emf.compare.tests.merge.MultipleMergeTest;
+import org.eclipse.emf.compare.tests.nodes.NodesPackage;
+import org.eclipse.emf.compare.tests.nodes.util.NodesResourceFactoryImpl;
+import org.eclipse.emf.compare.tests.postprocess.PostProcessorTest;
+import org.eclipse.emf.compare.tests.req.ReqComputingTest;
+import org.eclipse.emf.compare.tests.scope.DefaultComparisonScopeTest;
+import org.eclipse.emf.ecore.EPackage;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.junit.BeforeClass;
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+import org.junit.runners.Suite.SuiteClasses;
+
+/**
+ * This test suite allows us to launch all tests for EMF Compare at once.
+ * 
+ * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
+ */
+@RunWith(Suite.class)
+@SuiteClasses({CompareTestSuite.class, DefaultComparisonScopeTest.class, IdentifierComparisonTest.class,
+		ExtLibraryTest.class, ConflictDetectionTest.class, ReqComputingTest.class, EquiComputingTest.class,
+		DiffUtilTest.class, LCSPerformanceTest.class, MultipleMergeTest.class, PostProcessorTest.class,
+		IndividualMergeTest.class, ExtensionMergeTest.class, IndividualMergeOutOfScopeValuesTest.class,
+		ProximityComparisonTest.class, DynamicInstanceComparisonTest.class, URIDistanceTest.class,
+		FragmentationTest.class, AllEditTests.class, CommandStackTestSuite.class,
+		MatchEngineFactoryRegistryTest.class })
+public class AllTests {
+	/**
+	 * Standalone launcher for all of compare's tests.
+	 * 
+	 * @generated
+	 */
+	public static void main(String[] args) {
+		TestRunner.run(suite());
+	}
+
+	/**
+	 * This will return a suite populated with all tests available through this class.
+	 * 
+	 * @generated
+	 */
+	public static Test suite() {
+		return new JUnit4TestAdapter(CompareTestSuite.class);
+	}
+
+	@BeforeClass
+	public static void fillEMFRegistries() {
+		EPackage.Registry.INSTANCE.put(ComparePackage.eNS_URI, ComparePackage.eINSTANCE);
+		EPackage.Registry.INSTANCE.put(NodesPackage.eNS_URI, NodesPackage.eINSTANCE);
+
+		Resource.Factory.Registry.INSTANCE.getExtensionToFactoryMap().put("nodes", //$NON-NLS-1$
+				new NodesResourceFactoryImpl());
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare/META-INF/MANIFEST.MF b/plugins/org.eclipse.emf.compare/META-INF/MANIFEST.MF
index d9f07247e..4ac6f724b 100644
--- a/plugins/org.eclipse.emf.compare/META-INF/MANIFEST.MF
+++ b/plugins/org.eclipse.emf.compare/META-INF/MANIFEST.MF
@@ -18,6 +18,7 @@ Export-Package: org.eclipse.emf.compare,
  org.eclipse.emf.compare.match,
  org.eclipse.emf.compare.match.eobject,
  org.eclipse.emf.compare.match.eobject.internal;x-internal:=true,
+ org.eclipse.emf.compare.match.impl,
  org.eclipse.emf.compare.match.resource,
  org.eclipse.emf.compare.merge,
  org.eclipse.emf.compare.postprocessor,
diff --git a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/EMFCompare.java b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/EMFCompare.java
index 8c3a910ad..010e68848 100644
--- a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/EMFCompare.java
+++ b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/EMFCompare.java
@@ -1,344 +1,347 @@
-/*******************************************************************************

- * Copyright (c) 2012, 2013 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- * 

- * Contributors:

- *     Obeo - initial API and implementation

- *******************************************************************************/

-package org.eclipse.emf.compare;

-

-import static com.google.common.base.Preconditions.checkNotNull;

-

-import java.util.List;

-

-import org.eclipse.emf.common.notify.Notifier;

-import org.eclipse.emf.common.util.BasicMonitor;

-import org.eclipse.emf.common.util.Monitor;

-import org.eclipse.emf.compare.conflict.DefaultConflictDetector;

-import org.eclipse.emf.compare.conflict.IConflictDetector;

-import org.eclipse.emf.compare.diff.DefaultDiffEngine;

-import org.eclipse.emf.compare.diff.DiffBuilder;

-import org.eclipse.emf.compare.diff.IDiffEngine;

-import org.eclipse.emf.compare.equi.DefaultEquiEngine;

-import org.eclipse.emf.compare.equi.IEquiEngine;

-import org.eclipse.emf.compare.match.DefaultMatchEngine;

-import org.eclipse.emf.compare.match.IMatchEngine;

-import org.eclipse.emf.compare.postprocessor.IPostProcessor;

-import org.eclipse.emf.compare.postprocessor.PostProcessorDescriptorRegistryImpl;

-import org.eclipse.emf.compare.req.DefaultReqEngine;

-import org.eclipse.emf.compare.req.IReqEngine;

-import org.eclipse.emf.compare.scope.DefaultComparisonScope;

-import org.eclipse.emf.compare.scope.IComparisonScope;

-import org.eclipse.emf.compare.utils.UseIdentifiers;

-

-/**

- * This class serves as the main entry point of a comparison. When all that is wanted is a basic comparison of

- * two or three notifiers, a comparison using all of the default configuration can be launched through

- * <code>EMFCompare.builder().build().compare(EMFCompare.createDefaultScope(left, right, origin))</code>.

- * <p>

- * When in need of a more customized comparison, the API can be used through chained calls. For example, if

- * you need to compare two notifiers ({@code left} and {@code right}) while ignoring their identifiers, with a

- * given progress monitor (call it {@code progress}), you can do so through : <code>

- * EMFCompare.builder().setMatchEngine(DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(EMFCompare.createDefaultScope(left, right), new BasicMonitor())

- * </code>.

- * </p>

- * 

- * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>

- */

-public class EMFCompare {

-

-	/** The IMatchEngine to use to compute comparison. */

-	private final IMatchEngine matchEngine;

-

-	/** The IDiffEngine to use to compute comparison. */

-	private final IDiffEngine diffEngine;

-

-	/** The IReqEngine to use to compute comparison. */

-	private final IReqEngine reqEngine;

-

-	/** The IEquiEngine to use to compute comparison. */

-	private final IEquiEngine equiEngine;

-

-	/** The IConflictDetector to use to compute comparison. */

-	private final IConflictDetector conflictDetector;

-

-	/** The PostProcessorRegistry to use to find an IPostProcessor. */

-	private final IPostProcessor.Descriptor.Registry<?> postProcessorDescriptorRegistry;

-

-	/**

-	 * Creates a new EMFCompare object able to compare Notifier with the help of given engines.

-	 * 

-	 * @param matchEngine

-	 *            IMatchEngine to use to compute comparison

-	 * @param diffEngine

-	 *            IDiffEngine to use to compute comparison

-	 * @param reqEngine

-	 *            IReqEngine to use to compute comparison

-	 * @param equiEngine

-	 *            IEquiEngine to use to compute comparison

-	 * @param conflictDetector

-	 *            IConflictDetector to use to compute comparison

-	 * @param postProcessorFactoryRegistry

-	 *            PostProcessorRegistry to use to find an IPostProcessor

-	 */

-	protected EMFCompare(IMatchEngine matchEngine, IDiffEngine diffEngine, IReqEngine reqEngine,

-			IEquiEngine equiEngine, IConflictDetector conflictDetector,

-			IPostProcessor.Descriptor.Registry<?> postProcessorFactoryRegistry) {

-		this.matchEngine = checkNotNull(matchEngine);

-		this.diffEngine = checkNotNull(diffEngine);

-		this.reqEngine = checkNotNull(reqEngine);

-		this.equiEngine = checkNotNull(equiEngine);

-		this.conflictDetector = conflictDetector;

-		this.postProcessorDescriptorRegistry = checkNotNull(postProcessorFactoryRegistry);

-	}

-

-	/**

-	 * Creates a default comparison scope given its left and right notifiers.

-	 * <p>

-	 * The default comparison scope covers all proper content of the given notifiers, i.e any element

-	 * contained directly under that notifier.

-	 * </p>

-	 * 

-	 * @param left

-	 *            The left notifier of this scope.

-	 * @param right

-	 *            The right notifier of this scope.

-	 * @return The newly created scope, as used as default by EMF Compare.

-	 * @see DefaultComparisonScope

-	 */

-	public static IComparisonScope createDefaultScope(Notifier left, Notifier right) {

-		return new DefaultComparisonScope(left, right, null);

-	}

-

-	/**

-	 * Creates the default comparison scope given its left and right notifiers, along with the common ancestor

-	 * of both.

-	 * <p>

-	 * The default comparison scope covers all proper content of the given notifiers, i.e any element

-	 * contained directly under that notifier.

-	 * </p>

-	 * 

-	 * @param left

-	 *            The left notifier of this scope.

-	 * @param right

-	 *            The right notifier of this scope.

-	 * @param origin

-	 *            The common ancestor of {@code left} and {@code right}.

-	 * @return The newly created scope, as used as default by EMF Compare.

-	 * @see DefaultComparisonScope

-	 */

-	public static IComparisonScope createDefaultScope(Notifier left, Notifier right, Notifier origin) {

-		return new DefaultComparisonScope(left, right, origin);

-	}

-

-	/**

-	 * Computes and returns a new Comparison object representation the differences between Notifier in the

-	 * give {@code scope}.

-	 * 

-	 * @param scope

-	 *            the scope to compare.

-	 * @return the result of the comparison.

-	 */

-	public Comparison compare(IComparisonScope scope) {

-		return compare(scope, new BasicMonitor());

-	}

-

-	/**

-	 * Launches the comparison with the given scope and reporting progress to the given {@code monitor}.

-	 * 

-	 * @param scope

-	 *            the scope to compare.

-	 * @param monitor

-	 *            the monitor to report progress to.

-	 * @return the result of the comparison.

-	 */

-	public Comparison compare(IComparisonScope scope, final Monitor monitor) {

-		checkNotNull(scope);

-		checkNotNull(monitor);

-

-		final Comparison comparison = matchEngine.match(scope, monitor);

-

-		List<IPostProcessor> postProcessors = postProcessorDescriptorRegistry.getPostProcessors(scope);

-

-		for (IPostProcessor iPostProcessor : postProcessors) {

-			iPostProcessor.postMatch(comparison, monitor);

-		}

-

-		diffEngine.diff(comparison, monitor);

-

-		for (IPostProcessor iPostProcessor : postProcessors) {

-			iPostProcessor.postDiff(comparison, monitor);

-		}

-

-		reqEngine.computeRequirements(comparison, monitor);

-

-		for (IPostProcessor iPostProcessor : postProcessors) {

-			iPostProcessor.postRequirements(comparison, monitor);

-		}

-

-		equiEngine.computeEquivalences(comparison, monitor);

-

-		for (IPostProcessor iPostProcessor : postProcessors) {

-			iPostProcessor.postEquivalences(comparison, monitor);

-		}

-

-		if (comparison.isThreeWay() && conflictDetector != null) {

-			conflictDetector.detect(comparison, monitor);

-

-			for (IPostProcessor iPostProcessor : postProcessors) {

-				iPostProcessor.postConflicts(comparison, monitor);

-			}

-		}

-

-		for (IPostProcessor iPostProcessor : postProcessors) {

-			iPostProcessor.postComparison(comparison, monitor);

-		}

-

-		return comparison;

-	}

-

-	/**

-	 * Creates a new builder to configure the creation of a new EMFCompare object.

-	 * 

-	 * @return a new builder.

-	 */

-	public static Builder builder() {

-		return new Builder();

-	}

-

-	/**

-	 * A Builder pattern to instantiate EMFCompare objects.

-	 * 

-	 * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>

-	 */

-	public static class Builder {

-

-		/** The IMatchEngine to use to compute comparison. */

-		protected IMatchEngine matchEngine;

-

-		/** The IReqEngine to use to compute comparison. */

-		protected IReqEngine reqEngine;

-

-		/** The IDiffEngine to use to compute comparison. */

-		protected IDiffEngine diffEngine;

-

-		/** The IEquiEngine to use to compute comparison. */

-		protected IEquiEngine equiEngine;

-

-		/** The IConflictDetector to use to compute conflicts. */

-		protected IConflictDetector conflictDetector;

-

-		/** The PostProcessorRegistry to use to find an IPostProcessor. */

-		protected IPostProcessor.Descriptor.Registry<?> postProcessorRegistry;

-

-		/**

-		 * Creates a new builder object.

-		 */

-		protected Builder() {

-		}

-

-		/**

-		 * Sets the IMatchEngine to be used to compute Match.

-		 * 

-		 * @param me

-		 *            the IMatchEngine to be used to compute comparison.

-		 * @return this same builder to allow chained call.

-		 */

-		public Builder setMatchEngine(IMatchEngine me) {

-			this.matchEngine = checkNotNull(me);

-			return this;

-		}

-

-		/**

-		 * Sets the IDiffEngine to be used to compute Diff.

-		 * 

-		 * @param de

-		 *            the IDiffEngine to be used to compute Diff.

-		 * @return this same builder to allow chained call.

-		 */

-		public Builder setDiffEngine(IDiffEngine de) {

-			this.diffEngine = checkNotNull(de);

-			return this;

-		}

-

-		/**

-		 * Sets the IReqEngine to be used to compute dependencies between Diff.

-		 * 

-		 * @param re

-		 *            the IReqEngine to be used to compute dependencies between Diff.

-		 * @return this same builder to allow chained call.

-		 */

-		public Builder setRequirementEngine(IReqEngine re) {

-			this.reqEngine = checkNotNull(re);

-			return this;

-		}

-

-		/**

-		 * Sets the IEquiEngine to be used to compute equivalences between Diff.

-		 * 

-		 * @param ee

-		 *            the IEquiEngine to be used to compute equivalences between Diff

-		 * @return this same builder to allow chained call.

-		 */

-		public Builder setEquivalenceEngine(IEquiEngine ee) {

-			this.equiEngine = checkNotNull(ee);

-			return this;

-		}

-

-		/**

-		 * Sets the IEquiEngine to be used to compute conflicts between Diff.

-		 * 

-		 * @param cd

-		 *            the IEquiEngine to be used to compute conflicts between Diff.

-		 * @return this same builder to allow chained call.

-		 */

-		public Builder setConflictDetector(IConflictDetector cd) {

-			this.conflictDetector = checkNotNull(cd);

-			return this;

-		}

-

-		/**

-		 * Sets the PostProcessor to be used to find the post processor of each comparison steps.

-		 * 

-		 * @param r

-		 *            the PostProcessor to be used to find the post processor of each comparison steps.

-		 * @return this same builder to allow chained call.

-		 */

-		public Builder setPostProcessorRegistry(IPostProcessor.Descriptor.Registry<?> r) {

-			this.postProcessorRegistry = checkNotNull(r);

-			return this;

-		}

-

-		/**

-		 * Instantiates and return an EMFCompare object configured with the previously given engines.

-		 * 

-		 * @return an EMFCompare object configured with the previously given engines

-		 */

-		public EMFCompare build() {

-			if (matchEngine == null) {

-				matchEngine = DefaultMatchEngine.create(UseIdentifiers.WHEN_AVAILABLE);

-			}

-			if (diffEngine == null) {

-				diffEngine = new DefaultDiffEngine(new DiffBuilder());

-			}

-			if (reqEngine == null) {

-				reqEngine = new DefaultReqEngine();

-			}

-			if (equiEngine == null) {

-				equiEngine = new DefaultEquiEngine();

-			}

-			if (postProcessorRegistry == null) {

-				postProcessorRegistry = new PostProcessorDescriptorRegistryImpl<Object>();

-			}

-			if (conflictDetector == null) {

-				conflictDetector = new DefaultConflictDetector();

-			}

-			return new EMFCompare(this.matchEngine, this.diffEngine, this.reqEngine, this.equiEngine,

-					this.conflictDetector, this.postProcessorRegistry);

-		}

-	}

-

-}

+/*******************************************************************************
+ * Copyright (c) 2012, 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.List;
+
+import org.eclipse.emf.common.notify.Notifier;
+import org.eclipse.emf.common.util.BasicMonitor;
+import org.eclipse.emf.common.util.Monitor;
+import org.eclipse.emf.compare.conflict.DefaultConflictDetector;
+import org.eclipse.emf.compare.conflict.IConflictDetector;
+import org.eclipse.emf.compare.diff.DefaultDiffEngine;
+import org.eclipse.emf.compare.diff.DiffBuilder;
+import org.eclipse.emf.compare.diff.IDiffEngine;
+import org.eclipse.emf.compare.equi.DefaultEquiEngine;
+import org.eclipse.emf.compare.equi.IEquiEngine;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.match.impl.MatchEngineFactoryRegistryImpl;
+import org.eclipse.emf.compare.postprocessor.IPostProcessor;
+import org.eclipse.emf.compare.postprocessor.PostProcessorDescriptorRegistryImpl;
+import org.eclipse.emf.compare.req.DefaultReqEngine;
+import org.eclipse.emf.compare.req.IReqEngine;
+import org.eclipse.emf.compare.scope.DefaultComparisonScope;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+
+/**
+ * This class serves as the main entry point of a comparison. When all that is wanted is a basic comparison of
+ * two or three notifiers, a comparison using all of the default configuration can be launched through
+ * <code>EMFCompare.builder().build().compare(EMFCompare.createDefaultScope(left, right, origin))</code>.
+ * <p>
+ * When in need of a more customized comparison, the API can be used through chained calls. For example, if
+ * you need to compare two notifiers ({@code left} and {@code right}) while ignoring their identifiers, with a
+ * given progress monitor (call it {@code progress}), you can do so through : <code>
+ * EMFCompare.builder().setMatchEngine(DefaultMatchEngine.create(UseIdentifiers.NEVER)).build().compare(EMFCompare.createDefaultScope(left, right), new BasicMonitor())
+ * </code>.
+ * </p>
+ * 
+ * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
+ */
+public class EMFCompare {
+
+	/** The registry we'll use to create a match engine for this comparison. */
+	private final IMatchEngine.Factory.Registry matchEngineFactoryRegistry;
+
+	/** The IDiffEngine to use to compute comparison. */
+	private final IDiffEngine diffEngine;
+
+	/** The IReqEngine to use to compute comparison. */
+	private final IReqEngine reqEngine;
+
+	/** The IEquiEngine to use to compute comparison. */
+	private final IEquiEngine equiEngine;
+
+	/** The IConflictDetector to use to compute comparison. */
+	private final IConflictDetector conflictDetector;
+
+	/** The PostProcessorRegistry to use to find an IPostProcessor. */
+	private final IPostProcessor.Descriptor.Registry<?> postProcessorDescriptorRegistry;
+
+	/**
+	 * Creates a new EMFCompare object able to compare Notifier with the help of given engines.
+	 * 
+	 * @param matchEngineFactoryRegistry
+	 *            {@link IMatchEngine.Factory.Registry} to use to find a match engine factory to compute
+	 *            comparison
+	 * @param diffEngine
+	 *            IDiffEngine to use to compute comparison
+	 * @param reqEngine
+	 *            IReqEngine to use to compute comparison
+	 * @param equiEngine
+	 *            IEquiEngine to use to compute comparison
+	 * @param conflictDetector
+	 *            IConflictDetector to use to compute comparison
+	 * @param postProcessorFactoryRegistry
+	 *            PostProcessorRegistry to use to find an IPostProcessor
+	 */
+	protected EMFCompare(IMatchEngine.Factory.Registry matchEngineFactoryRegistry, IDiffEngine diffEngine,
+			IReqEngine reqEngine, IEquiEngine equiEngine, IConflictDetector conflictDetector,
+			IPostProcessor.Descriptor.Registry<?> postProcessorFactoryRegistry) {
+		this.matchEngineFactoryRegistry = checkNotNull(matchEngineFactoryRegistry);
+		this.diffEngine = checkNotNull(diffEngine);
+		this.reqEngine = checkNotNull(reqEngine);
+		this.equiEngine = checkNotNull(equiEngine);
+		this.conflictDetector = conflictDetector;
+		this.postProcessorDescriptorRegistry = checkNotNull(postProcessorFactoryRegistry);
+	}
+
+	/**
+	 * Creates a default comparison scope given its left and right notifiers.
+	 * <p>
+	 * The default comparison scope covers all proper content of the given notifiers, i.e any element
+	 * contained directly under that notifier.
+	 * </p>
+	 * 
+	 * @param left
+	 *            The left notifier of this scope.
+	 * @param right
+	 *            The right notifier of this scope.
+	 * @return The newly created scope, as used as default by EMF Compare.
+	 * @see DefaultComparisonScope
+	 */
+	public static IComparisonScope createDefaultScope(Notifier left, Notifier right) {
+		return new DefaultComparisonScope(left, right, null);
+	}
+
+	/**
+	 * Creates the default comparison scope given its left and right notifiers, along with the common ancestor
+	 * of both.
+	 * <p>
+	 * The default comparison scope covers all proper content of the given notifiers, i.e any element
+	 * contained directly under that notifier.
+	 * </p>
+	 * 
+	 * @param left
+	 *            The left notifier of this scope.
+	 * @param right
+	 *            The right notifier of this scope.
+	 * @param origin
+	 *            The common ancestor of {@code left} and {@code right}.
+	 * @return The newly created scope, as used as default by EMF Compare.
+	 * @see DefaultComparisonScope
+	 */
+	public static IComparisonScope createDefaultScope(Notifier left, Notifier right, Notifier origin) {
+		return new DefaultComparisonScope(left, right, origin);
+	}
+
+	/**
+	 * Computes and returns a new Comparison object representation the differences between Notifier in the
+	 * give {@code scope}.
+	 * 
+	 * @param scope
+	 *            the scope to compare.
+	 * @return the result of the comparison.
+	 */
+	public Comparison compare(IComparisonScope scope) {
+		return compare(scope, new BasicMonitor());
+	}
+
+	/**
+	 * Launches the comparison with the given scope and reporting progress to the given {@code monitor}.
+	 * 
+	 * @param scope
+	 *            the scope to compare.
+	 * @param monitor
+	 *            the monitor to report progress to.
+	 * @return the result of the comparison.
+	 */
+	public Comparison compare(IComparisonScope scope, final Monitor monitor) {
+		checkNotNull(scope);
+		checkNotNull(monitor);
+
+		final Comparison comparison = matchEngineFactoryRegistry.getHighestRankingMatchEngineFactory(scope)
+				.getMatchEngine().match(scope, monitor);
+
+		List<IPostProcessor> postProcessors = postProcessorDescriptorRegistry.getPostProcessors(scope);
+
+		for (IPostProcessor iPostProcessor : postProcessors) {
+			iPostProcessor.postMatch(comparison, monitor);
+		}
+
+		diffEngine.diff(comparison, monitor);
+
+		for (IPostProcessor iPostProcessor : postProcessors) {
+			iPostProcessor.postDiff(comparison, monitor);
+		}
+
+		reqEngine.computeRequirements(comparison, monitor);
+
+		for (IPostProcessor iPostProcessor : postProcessors) {
+			iPostProcessor.postRequirements(comparison, monitor);
+		}
+
+		equiEngine.computeEquivalences(comparison, monitor);
+
+		for (IPostProcessor iPostProcessor : postProcessors) {
+			iPostProcessor.postEquivalences(comparison, monitor);
+		}
+
+		if (comparison.isThreeWay() && conflictDetector != null) {
+			conflictDetector.detect(comparison, monitor);
+
+			for (IPostProcessor iPostProcessor : postProcessors) {
+				iPostProcessor.postConflicts(comparison, monitor);
+			}
+		}
+
+		for (IPostProcessor iPostProcessor : postProcessors) {
+			iPostProcessor.postComparison(comparison, monitor);
+		}
+
+		return comparison;
+	}
+
+	/**
+	 * Creates a new builder to configure the creation of a new EMFCompare object.
+	 * 
+	 * @return a new builder.
+	 */
+	public static Builder builder() {
+		return new Builder();
+	}
+
+	/**
+	 * A Builder pattern to instantiate EMFCompare objects.
+	 * 
+	 * @author <a href="mailto:mikael.barbero@obeo.fr">Mikael Barbero</a>
+	 */
+	public static class Builder {
+
+		/** The registry we'll use to create a match engine for this comparison. */
+		protected IMatchEngine.Factory.Registry matchEngineFactoryRegistry;
+
+		/** The IReqEngine to use to compute comparison. */
+		protected IReqEngine reqEngine;
+
+		/** The IDiffEngine to use to compute comparison. */
+		protected IDiffEngine diffEngine;
+
+		/** The IEquiEngine to use to compute comparison. */
+		protected IEquiEngine equiEngine;
+
+		/** The IConflictDetector to use to compute conflicts. */
+		protected IConflictDetector conflictDetector;
+
+		/** The PostProcessorRegistry to use to find an IPostProcessor. */
+		protected IPostProcessor.Descriptor.Registry<?> registry;
+
+		/**
+		 * Creates a new builder object.
+		 */
+		protected Builder() {
+		}
+
+		/**
+		 * Sets the IMatchEngine.Factory.Registry to be used to find a match engine factory to compute
+		 * comparison.
+		 * 
+		 * @param mefr
+		 *            the IMatchEngine.Factory.Registry to be used to find a match engine factory to compute
+		 *            comparison.
+		 * @return this same builder to allow chained call.
+		 */
+		public Builder setMatchEngineFactoryRegistry(IMatchEngine.Factory.Registry mefr) {
+			this.matchEngineFactoryRegistry = checkNotNull(mefr);
+			return this;
+		}
+
+		/**
+		 * Sets the IDiffEngine to be used to compute Diff.
+		 * 
+		 * @param de
+		 *            the IDiffEngine to be used to compute Diff.
+		 * @return this same builder to allow chained call.
+		 */
+		public Builder setDiffEngine(IDiffEngine de) {
+			this.diffEngine = checkNotNull(de);
+			return this;
+		}
+
+		/**
+		 * Sets the IReqEngine to be used to compute dependencies between Diff.
+		 * 
+		 * @param re
+		 *            the IReqEngine to be used to compute dependencies between Diff.
+		 * @return this same builder to allow chained call.
+		 */
+		public Builder setRequirementEngine(IReqEngine re) {
+			this.reqEngine = checkNotNull(re);
+			return this;
+		}
+
+		/**
+		 * Sets the IEquiEngine to be used to compute equivalences between Diff.
+		 * 
+		 * @param ee
+		 *            the IEquiEngine to be used to compute equivalences between Diff
+		 * @return this same builder to allow chained call.
+		 */
+		public Builder setEquivalenceEngine(IEquiEngine ee) {
+			this.equiEngine = checkNotNull(ee);
+			return this;
+		}
+
+		/**
+		 * Sets the IEquiEngine to be used to compute conflicts between Diff.
+		 * 
+		 * @param cd
+		 *            the IEquiEngine to be used to compute conflicts between Diff.
+		 * @return this same builder to allow chained call.
+		 */
+		public Builder setConflictDetector(IConflictDetector cd) {
+			this.conflictDetector = checkNotNull(cd);
+			return this;
+		}
+
+		/**
+		 * Sets the PostProcessor to be used to find the post processor of each comparison steps.
+		 * 
+		 * @param r
+		 *            the PostProcessor to be used to find the post processor of each comparison steps.
+		 * @return this same builder to allow chained call.
+		 */
+		public Builder setPostProcessorRegistry(IPostProcessor.Descriptor.Registry<?> r) {
+			this.registry = checkNotNull(r);
+			return this;
+		}
+
+		/**
+		 * Instantiates and return an EMFCompare object configured with the previously given engines.
+		 * 
+		 * @return an EMFCompare object configured with the previously given engines
+		 */
+		public EMFCompare build() {
+			if (matchEngineFactoryRegistry == null) {
+				matchEngineFactoryRegistry = MatchEngineFactoryRegistryImpl.createStandaloneInstance();
+			}
+			if (diffEngine == null) {
+				diffEngine = new DefaultDiffEngine(new DiffBuilder());
+			}
+			if (reqEngine == null) {
+				reqEngine = new DefaultReqEngine();
+			}
+			if (equiEngine == null) {
+				equiEngine = new DefaultEquiEngine();
+			}
+			if (registry == null) {
+				registry = new PostProcessorDescriptorRegistryImpl();
+			}
+			if (conflictDetector == null) {
+				conflictDetector = new DefaultConflictDetector();
+			}
+			return new EMFCompare(this.matchEngineFactoryRegistry, this.diffEngine, this.reqEngine,
+					this.equiEngine, this.conflictDetector, this.registry);
+		}
+	}
+
+}
diff --git a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/DefaultMatchEngine.java b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/DefaultMatchEngine.java
index 5e23d5e2a..68eaca20b 100644
--- a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/DefaultMatchEngine.java
+++ b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/DefaultMatchEngine.java
@@ -1,397 +1,399 @@
-/*******************************************************************************

- * Copyright (c) 2012 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- *

- * Contributors:

- *     Obeo - initial API and implementation

- *     Eike Stepper - (390846) Make the DefaultMatchEngine more extensible

- *******************************************************************************/

-package org.eclipse.emf.compare.match;

-

-import static com.google.common.base.Preconditions.checkNotNull;

-

-import com.google.common.collect.Iterators;

-import com.google.common.collect.Lists;

-

-import java.util.Iterator;

-import java.util.List;

-

-import org.eclipse.emf.common.notify.Notifier;

-import org.eclipse.emf.common.util.Monitor;

-import org.eclipse.emf.common.util.URI;

-import org.eclipse.emf.compare.CompareFactory;

-import org.eclipse.emf.compare.Comparison;

-import org.eclipse.emf.compare.MatchResource;

-import org.eclipse.emf.compare.match.eobject.EditionDistance;

-import org.eclipse.emf.compare.match.eobject.IEObjectMatcher;

-import org.eclipse.emf.compare.match.eobject.IdentifierEObjectMatcher;

-import org.eclipse.emf.compare.match.eobject.ProximityEObjectMatcher;

-import org.eclipse.emf.compare.match.resource.IResourceMatcher;

-import org.eclipse.emf.compare.match.resource.StrategyResourceMatcher;

-import org.eclipse.emf.compare.scope.IComparisonScope;

-import org.eclipse.emf.compare.utils.UseIdentifiers;

-import org.eclipse.emf.ecore.EObject;

-import org.eclipse.emf.ecore.resource.Resource;

-import org.eclipse.emf.ecore.resource.ResourceSet;

-

-/**

- * The Match engine orchestrates the matching process : it takes an {@link IComparisonScope scope} as input,

- * iterates over its {@link IComparisonScope#getLeft() left}, {@link IComparisonScope#getRight() right} and

- * {@link IComparisonScope#getOrigin() origin} roots and delegates to {@link IResourceMatcher}s and

- * {@link IEObjectMatcher}s in order to create the result {@link Comparison} model for this scope.

- * 

- * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>

- */

-public class DefaultMatchEngine implements IMatchEngine {

-

-	/**

-	 * Default max size of the EObject's URI loading cache.

-	 */

-	public static final int DEFAULT_EOBJECT_URI_CACHE_MAX_SIZE = 1024;

-

-	/** The delegate {@link IEObjectMatcher matcher} that will actually pair EObjects together. */

-	private final IEObjectMatcher eObjectMatcher;

-

-	/** The factory that will be use to instantiate Comparison as return by match() methods. */

-	private final IComparisonFactory comparisonFactory;

-

-	/**

-	 * This default engine delegates the pairing of EObjects to an {@link IEObjectMatcher}.

-	 * 

-	 * @param matcher

-	 *            The matcher that will be in charge of pairing EObjects together for this comparison process.

-	 * @param comparisonFactory

-	 *            factory that will be use to instantiate Comparison as return by match() methods.

-	 */

-	public DefaultMatchEngine(IEObjectMatcher matcher, IComparisonFactory comparisonFactory) {

-		this.eObjectMatcher = checkNotNull(matcher);

-		this.comparisonFactory = checkNotNull(comparisonFactory);

-	}

-

-	/**

-	 * {@inheritDoc}

-	 * 

-	 * @see org.eclipse.emf.compare.match.IMatchEngine#match(org.eclipse.emf.compare.scope.IComparisonScope,

-	 *      org.eclipse.emf.common.util.Monitor)

-	 */

-	public Comparison match(IComparisonScope scope, Monitor monitor) {

-		Comparison comparison = comparisonFactory.createComparison();

-

-		final Notifier left = scope.getLeft();

-		final Notifier right = scope.getRight();

-		final Notifier origin = scope.getOrigin();

-

-		comparison.setThreeWay(origin != null);

-

-		match(comparison, scope, left, right, origin, monitor);

-

-		return comparison;

-	}

-

-	/**

-	 * This methods will delegate to the proper "match(T, T, T)" implementation according to the types of

-	 * {@code left}, {@code right} and {@code origin}.

-	 * 

-	 * @param comparison

-	 *            The comparison to which will be added detected matches.

-	 * @param scope

-	 *            The comparison scope that should be used by this engine to determine the objects to match.

-	 * @param left

-	 *            The left {@link Notifier}.

-	 * @param right

-	 *            The right {@link Notifier}.

-	 * @param origin

-	 *            The common ancestor of <code>left</code> and <code>right</code>. Can be <code>null</code>.

-	 * @param monitor

-	 *            The monitor to report progress or to check for cancellation

-	 */

-	protected void match(Comparison comparison, IComparisonScope scope, final Notifier left,

-			final Notifier right, final Notifier origin, Monitor monitor) {

-		// FIXME side-effect coding

-		if (left instanceof ResourceSet || right instanceof ResourceSet) {

-			match(comparison, scope, (ResourceSet)left, (ResourceSet)right, (ResourceSet)origin, monitor);

-		} else if (left instanceof Resource || right instanceof Resource) {

-			match(comparison, scope, (Resource)left, (Resource)right, (Resource)origin, monitor);

-		} else if (left instanceof EObject || right instanceof EObject) {

-			match(comparison, scope, (EObject)left, (EObject)right, (EObject)origin, monitor);

-		} else {

-			// TODO Cannot happen ... for now. Should we log an exception?

-		}

-	}

-

-	/**

-	 * This will be used to match the given {@link ResourceSet}s. This default implementation will query the

-	 * comparison scope for these resource sets children, then delegate to an {@link IResourceMatcher} to

-	 * determine the resource mappings.

-	 * 

-	 * @param comparison

-	 *            The comparison to which will be added detected matches.

-	 * @param scope

-	 *            The comparison scope that should be used by this engine to determine the objects to match.

-	 * @param left

-	 *            The left {@link ResourceSet}.

-	 * @param right

-	 *            The right {@link ResourceSet}.

-	 * @param origin

-	 *            The common ancestor of <code>left</code> and <code>right</code>. Can be <code>null</code>.

-	 * @param monitor

-	 *            The monitor to report progress or to check for cancellation

-	 */

-	protected void match(Comparison comparison, IComparisonScope scope, ResourceSet left, ResourceSet right,

-			ResourceSet origin, Monitor monitor) {

-		final Iterator<? extends Resource> leftChildren = scope.getCoveredResources(left);

-		final Iterator<? extends Resource> rightChildren = scope.getCoveredResources(right);

-		final Iterator<? extends Resource> originChildren;

-		if (origin != null) {

-			originChildren = scope.getCoveredResources(origin);

-		} else {

-			originChildren = Iterators.emptyIterator();

-		}

-

-		final IResourceMatcher resourceMatcher = createResourceMatcher();

-		final Iterable<MatchResource> mappings = resourceMatcher.createMappings(leftChildren, rightChildren,

-				originChildren);

-

-		final List<Iterator<? extends EObject>> leftIterators = Lists.newLinkedList();

-		final List<Iterator<? extends EObject>> rightIterators = Lists.newLinkedList();

-		final List<Iterator<? extends EObject>> originIterators = Lists.newLinkedList();

-

-		for (MatchResource mapping : mappings) {

-			comparison.getMatchedResources().add(mapping);

-

-			final Resource leftRes = mapping.getLeft();

-			final Resource rightRes = mapping.getRight();

-			final Resource originRes = mapping.getOrigin();

-

-			if (leftRes != null) {

-				leftIterators.add(scope.getCoveredEObjects(leftRes));

-			}

-

-			if (rightRes != null) {

-				rightIterators.add(scope.getCoveredEObjects(rightRes));

-			}

-

-			if (originRes != null) {

-				originIterators.add(scope.getCoveredEObjects(originRes));

-			}

-		}

-

-		final Iterator<? extends EObject> leftEObjects = Iterators.concat(leftIterators.iterator());

-		final Iterator<? extends EObject> rightEObjects = Iterators.concat(rightIterators.iterator());

-		final Iterator<? extends EObject> originEObjects = Iterators.concat(originIterators.iterator());

-

-		getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects, monitor);

-	}

-

-	/**

-	 * This will only query the scope for the given Resources' children, then delegate to an

-	 * {@link IEObjectMatcher} to determine the EObject matches.

-	 * <p>

-	 * We expect at least two of the given resources not to be <code>null</code>.

-	 * </p>

-	 * 

-	 * @param comparison

-	 *            The comparison to which will be added detected matches.

-	 * @param scope

-	 *            The comparison scope that should be used by this engine to determine the objects to match.

-	 * @param left

-	 *            The left {@link Resource}. Can be <code>null</code>.

-	 * @param right

-	 *            The right {@link Resource}. Can be <code>null</code>.

-	 * @param origin

-	 *            The common ancestor of <code>left</code> and <code>right</code>. Can be <code>null</code>.

-	 * @param monitor

-	 *            The monitor to report progress or to check for cancellation

-	 */

-	protected void match(Comparison comparison, IComparisonScope scope, Resource left, Resource right,

-			Resource origin, Monitor monitor) {

-		// Our "roots" are Resources. Consider them matched

-		final MatchResource match = CompareFactory.eINSTANCE.createMatchResource();

-

-		match.setLeft(left);

-		match.setRight(right);

-		match.setOrigin(origin);

-

-		if (left != null) {

-			URI uri = left.getURI();

-			if (uri != null) {

-				match.setLeftURI(uri.toString());

-			}

-		}

-

-		if (right != null) {

-			URI uri = right.getURI();

-			if (uri != null) {

-				match.setRightURI(uri.toString());

-			}

-		}

-

-		if (origin != null) {

-			URI uri = origin.getURI();

-			if (uri != null) {

-				match.setOriginURI(uri.toString());

-			}

-		}

-

-		comparison.getMatchedResources().add(match);

-

-		// We need at least two resources to match them

-		if (atLeastTwo(left == null, right == null, origin == null)) {

-			/*

-			 * TODO But if we have only one resource, which is then unmatched, should we not still do

-			 * something with it?

-			 */

-			return;

-		}

-

-		final Iterator<? extends EObject> leftEObjects;

-		if (left != null) {

-			leftEObjects = scope.getCoveredEObjects(left);

-		} else {

-			leftEObjects = Iterators.emptyIterator();

-		}

-		final Iterator<? extends EObject> rightEObjects;

-		if (right != null) {

-			rightEObjects = scope.getCoveredEObjects(right);

-		} else {

-			rightEObjects = Iterators.emptyIterator();

-		}

-		final Iterator<? extends EObject> originEObjects;

-		if (origin != null) {

-			originEObjects = scope.getCoveredEObjects(origin);

-		} else {

-			originEObjects = Iterators.emptyIterator();

-		}

-

-		getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects, monitor);

-

-	}

-

-	/**

-	 * This will query the scope for the given {@link EObject}s' children, then delegate to an

-	 * {@link IEObjectMatcher} to compute the Matches.

-	 * <p>

-	 * We expect at least the <code>left</code> and <code>right</code> EObjects not to be <code>null</code>.

-	 * </p>

-	 * 

-	 * @param comparison

-	 *            The comparison to which will be added detected matches.

-	 * @param scope

-	 *            The comparison scope that should be used by this engine to determine the objects to match.

-	 * @param left

-	 *            The left {@link EObject}.

-	 * @param right

-	 *            The right {@link EObject}.

-	 * @param origin

-	 *            The common ancestor of <code>left</code> and <code>right</code>.

-	 * @param monitor

-	 *            The monitor to report progress or to check for cancellation.

-	 */

-	protected void match(Comparison comparison, IComparisonScope scope, EObject left, EObject right,

-			EObject origin, Monitor monitor) {

-		if (left == null || right == null) {

-			throw new IllegalArgumentException();

-		}

-

-		final Iterator<? extends EObject> leftEObjects = Iterators.concat(Iterators.singletonIterator(left),

-				scope.getChildren(left));

-		final Iterator<? extends EObject> rightEObjects = Iterators.concat(

-				Iterators.singletonIterator(right), scope.getChildren(right));

-		final Iterator<? extends EObject> originEObjects;

-		if (origin != null) {

-			originEObjects = Iterators.concat(Iterators.singletonIterator(origin), scope.getChildren(origin));

-		} else {

-			originEObjects = Iterators.emptyIterator();

-		}

-

-		getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects, monitor);

-	}

-

-	/**

-	 * This will be used to create the resource matcher that will be used by this match engine.

-	 * 

-	 * @return An {@link IResourceMatcher} that can be used to retrieve the {@link MatchResource}s for this

-	 *         comparison.

-	 */

-	protected IResourceMatcher createResourceMatcher() {

-		return new StrategyResourceMatcher();

-	}

-

-	/**

-	 * Returns the EObject matcher associated with this match engine.

-	 * 

-	 * @return The EObject matcher associated with this match engine.

-	 */

-	protected final IEObjectMatcher getEObjectMatcher() {

-		return eObjectMatcher;

-	}

-

-	/**

-	 * This will check that at least two of the three given booleans are <code>true</code>.

-	 * 

-	 * @param condition1

-	 *            First of the three booleans.

-	 * @param condition2

-	 *            Second of the three booleans.

-	 * @param condition3

-	 *            Third of the three booleans.

-	 * @return <code>true</code> if at least two of the three given booleans are <code>true</code>,

-	 *         <code>false</code> otherwise.

-	 */

-	private static boolean atLeastTwo(boolean condition1, boolean condition2, boolean condition3) {

-		// CHECKSTYLE:OFF This expression is alone in its method, and documented.

-		return condition1 && (condition2 || condition3) || (condition2 && condition3);

-		// CHECKSTYLE:ON

-	}

-

-	/**

-	 * Helper creator method that instantiate a {@link DefaultMatchEngine} that will use identifiers as

-	 * specified by the given {@code useIDs} enumeration.

-	 * 

-	 * @param useIDs

-	 *            the kinds of matcher to use.

-	 * @return a new {@link DefaultMatchEngine} instance.

-	 */

-	public static IMatchEngine create(UseIdentifiers useIDs) {

-		final IComparisonFactory comparisonFactory = new DefaultComparisonFactory(

-				new DefaultEqualityHelperFactory());

-		final IEObjectMatcher matcher = createDefaultEObjectMatcher(useIDs);

-

-		final IMatchEngine matchEngine = new DefaultMatchEngine(matcher, comparisonFactory);

-		return matchEngine;

-	}

-

-	/**

-	 * Creates and configures an {@link IEObjectMatcher} with the strategy given by {@code useIDs}. The

-	 * {@code cache} will be used to cache some expensive computation (should better a LoadingCache).

-	 * 

-	 * @param useIDs

-	 *            which strategy the return IEObjectMatcher must follow.

-	 * @return a new IEObjectMatcher.

-	 */

-	public static IEObjectMatcher createDefaultEObjectMatcher(UseIdentifiers useIDs) {

-		final IEObjectMatcher matcher;

-		final EditionDistance editionDistance = new EditionDistance();

-		switch (useIDs) {

-			case NEVER:

-				matcher = new ProximityEObjectMatcher(editionDistance);

-				break;

-			case ONLY:

-				matcher = new IdentifierEObjectMatcher();

-				break;

-			case WHEN_AVAILABLE:

-				// fall through to default

-			default:

-				// Use an ID matcher, delegating to proximity when no ID is available

-				final IEObjectMatcher contentMatcher = new ProximityEObjectMatcher(editionDistance);

-				matcher = new IdentifierEObjectMatcher(contentMatcher);

-				break;

-

-		}

-

-		return matcher;

-	}

-}

+/*******************************************************************************
+ * Copyright (c) 2012, 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *     Eike Stepper - (390846) Make the DefaultMatchEngine more extensible
+ *******************************************************************************/
+package org.eclipse.emf.compare.match;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.collect.Iterators;
+import com.google.common.collect.Lists;
+
+import java.util.Iterator;
+import java.util.List;
+
+import org.eclipse.emf.common.notify.Notifier;
+import org.eclipse.emf.common.util.Monitor;
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.compare.CompareFactory;
+import org.eclipse.emf.compare.Comparison;
+import org.eclipse.emf.compare.MatchResource;
+import org.eclipse.emf.compare.match.eobject.EditionDistance;
+import org.eclipse.emf.compare.match.eobject.IEObjectMatcher;
+import org.eclipse.emf.compare.match.eobject.IdentifierEObjectMatcher;
+import org.eclipse.emf.compare.match.eobject.ProximityEObjectMatcher;
+import org.eclipse.emf.compare.match.resource.IResourceMatcher;
+import org.eclipse.emf.compare.match.resource.StrategyResourceMatcher;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+import org.eclipse.emf.compare.utils.UseIdentifiers;
+import org.eclipse.emf.ecore.EObject;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+
+/**
+ * The Match engine orchestrates the matching process : it takes an {@link IComparisonScope scope} as input,
+ * iterates over its {@link IComparisonScope#getLeft() left}, {@link IComparisonScope#getRight() right} and
+ * {@link IComparisonScope#getOrigin() origin} roots and delegates to {@link IResourceMatcher}s and
+ * {@link IEObjectMatcher}s in order to create the result {@link Comparison} model for this scope.
+ * 
+ * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
+ */
+public class DefaultMatchEngine implements IMatchEngine {
+
+	/**
+	 * Default max size of the EObject's URI loading cache.
+	 */
+	public static final int DEFAULT_EOBJECT_URI_CACHE_MAX_SIZE = 1024;
+
+	/** The delegate {@link IEObjectMatcher matcher} that will actually pair EObjects together. */
+	private final IEObjectMatcher eObjectMatcher;
+
+	/** The factory that will be use to instantiate Comparison as return by match() methods. */
+	private final IComparisonFactory comparisonFactory;
+
+	/**
+	 * This default engine delegates the pairing of EObjects to an {@link IEObjectMatcher}.
+	 * 
+	 * @param matcher
+	 *            The matcher that will be in charge of pairing EObjects together for this comparison process.
+	 * @param comparisonFactory
+	 *            factory that will be use to instantiate Comparison as return by match() methods.
+	 * @since 3.0
+	 */
+	public DefaultMatchEngine(IEObjectMatcher matcher, IComparisonFactory comparisonFactory) {
+		this.eObjectMatcher = checkNotNull(matcher);
+		this.comparisonFactory = checkNotNull(comparisonFactory);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine#match(org.eclipse.emf.compare.scope.IComparisonScope,
+	 *      org.eclipse.emf.common.util.Monitor)
+	 */
+	public Comparison match(IComparisonScope scope, Monitor monitor) {
+		Comparison comparison = comparisonFactory.createComparison();
+
+		final Notifier left = scope.getLeft();
+		final Notifier right = scope.getRight();
+		final Notifier origin = scope.getOrigin();
+
+		comparison.setThreeWay(origin != null);
+
+		match(comparison, scope, left, right, origin, monitor);
+
+		return comparison;
+	}
+
+	/**
+	 * This methods will delegate to the proper "match(T, T, T)" implementation according to the types of
+	 * {@code left}, {@code right} and {@code origin}.
+	 * 
+	 * @param comparison
+	 *            The comparison to which will be added detected matches.
+	 * @param scope
+	 *            The comparison scope that should be used by this engine to determine the objects to match.
+	 * @param left
+	 *            The left {@link Notifier}.
+	 * @param right
+	 *            The right {@link Notifier}.
+	 * @param origin
+	 *            The common ancestor of <code>left</code> and <code>right</code>. Can be <code>null</code>.
+	 * @param monitor
+	 *            The monitor to report progress or to check for cancellation
+	 */
+	protected void match(Comparison comparison, IComparisonScope scope, final Notifier left,
+			final Notifier right, final Notifier origin, Monitor monitor) {
+		// FIXME side-effect coding
+		if (left instanceof ResourceSet || right instanceof ResourceSet) {
+			match(comparison, scope, (ResourceSet)left, (ResourceSet)right, (ResourceSet)origin, monitor);
+		} else if (left instanceof Resource || right instanceof Resource) {
+			match(comparison, scope, (Resource)left, (Resource)right, (Resource)origin, monitor);
+		} else if (left instanceof EObject || right instanceof EObject) {
+			match(comparison, scope, (EObject)left, (EObject)right, (EObject)origin, monitor);
+		} else {
+			// TODO Cannot happen ... for now. Should we log an exception?
+		}
+	}
+
+	/**
+	 * This will be used to match the given {@link ResourceSet}s. This default implementation will query the
+	 * comparison scope for these resource sets children, then delegate to an {@link IResourceMatcher} to
+	 * determine the resource mappings.
+	 * 
+	 * @param comparison
+	 *            The comparison to which will be added detected matches.
+	 * @param scope
+	 *            The comparison scope that should be used by this engine to determine the objects to match.
+	 * @param left
+	 *            The left {@link ResourceSet}.
+	 * @param right
+	 *            The right {@link ResourceSet}.
+	 * @param origin
+	 *            The common ancestor of <code>left</code> and <code>right</code>. Can be <code>null</code>.
+	 * @param monitor
+	 *            The monitor to report progress or to check for cancellation
+	 */
+	protected void match(Comparison comparison, IComparisonScope scope, ResourceSet left, ResourceSet right,
+			ResourceSet origin, Monitor monitor) {
+		final Iterator<? extends Resource> leftChildren = scope.getCoveredResources(left);
+		final Iterator<? extends Resource> rightChildren = scope.getCoveredResources(right);
+		final Iterator<? extends Resource> originChildren;
+		if (origin != null) {
+			originChildren = scope.getCoveredResources(origin);
+		} else {
+			originChildren = Iterators.emptyIterator();
+		}
+
+		final IResourceMatcher resourceMatcher = createResourceMatcher();
+		final Iterable<MatchResource> mappings = resourceMatcher.createMappings(leftChildren, rightChildren,
+				originChildren);
+
+		final List<Iterator<? extends EObject>> leftIterators = Lists.newLinkedList();
+		final List<Iterator<? extends EObject>> rightIterators = Lists.newLinkedList();
+		final List<Iterator<? extends EObject>> originIterators = Lists.newLinkedList();
+
+		for (MatchResource mapping : mappings) {
+			comparison.getMatchedResources().add(mapping);
+
+			final Resource leftRes = mapping.getLeft();
+			final Resource rightRes = mapping.getRight();
+			final Resource originRes = mapping.getOrigin();
+
+			if (leftRes != null) {
+				leftIterators.add(scope.getCoveredEObjects(leftRes));
+			}
+
+			if (rightRes != null) {
+				rightIterators.add(scope.getCoveredEObjects(rightRes));
+			}
+
+			if (originRes != null) {
+				originIterators.add(scope.getCoveredEObjects(originRes));
+			}
+		}
+
+		final Iterator<? extends EObject> leftEObjects = Iterators.concat(leftIterators.iterator());
+		final Iterator<? extends EObject> rightEObjects = Iterators.concat(rightIterators.iterator());
+		final Iterator<? extends EObject> originEObjects = Iterators.concat(originIterators.iterator());
+
+		getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects, monitor);
+	}
+
+	/**
+	 * This will only query the scope for the given Resources' children, then delegate to an
+	 * {@link IEObjectMatcher} to determine the EObject matches.
+	 * <p>
+	 * We expect at least two of the given resources not to be <code>null</code>.
+	 * </p>
+	 * 
+	 * @param comparison
+	 *            The comparison to which will be added detected matches.
+	 * @param scope
+	 *            The comparison scope that should be used by this engine to determine the objects to match.
+	 * @param left
+	 *            The left {@link Resource}. Can be <code>null</code>.
+	 * @param right
+	 *            The right {@link Resource}. Can be <code>null</code>.
+	 * @param origin
+	 *            The common ancestor of <code>left</code> and <code>right</code>. Can be <code>null</code>.
+	 * @param monitor
+	 *            The monitor to report progress or to check for cancellation
+	 */
+	protected void match(Comparison comparison, IComparisonScope scope, Resource left, Resource right,
+			Resource origin, Monitor monitor) {
+		// Our "roots" are Resources. Consider them matched
+		final MatchResource match = CompareFactory.eINSTANCE.createMatchResource();
+
+		match.setLeft(left);
+		match.setRight(right);
+		match.setOrigin(origin);
+
+		if (left != null) {
+			URI uri = left.getURI();
+			if (uri != null) {
+				match.setLeftURI(uri.toString());
+			}
+		}
+
+		if (right != null) {
+			URI uri = right.getURI();
+			if (uri != null) {
+				match.setRightURI(uri.toString());
+			}
+		}
+
+		if (origin != null) {
+			URI uri = origin.getURI();
+			if (uri != null) {
+				match.setOriginURI(uri.toString());
+			}
+		}
+
+		comparison.getMatchedResources().add(match);
+
+		// We need at least two resources to match them
+		if (atLeastTwo(left == null, right == null, origin == null)) {
+			/*
+			 * TODO But if we have only one resource, which is then unmatched, should we not still do
+			 * something with it?
+			 */
+			return;
+		}
+
+		final Iterator<? extends EObject> leftEObjects;
+		if (left != null) {
+			leftEObjects = scope.getCoveredEObjects(left);
+		} else {
+			leftEObjects = Iterators.emptyIterator();
+		}
+		final Iterator<? extends EObject> rightEObjects;
+		if (right != null) {
+			rightEObjects = scope.getCoveredEObjects(right);
+		} else {
+			rightEObjects = Iterators.emptyIterator();
+		}
+		final Iterator<? extends EObject> originEObjects;
+		if (origin != null) {
+			originEObjects = scope.getCoveredEObjects(origin);
+		} else {
+			originEObjects = Iterators.emptyIterator();
+		}
+
+		getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects, monitor);
+
+	}
+
+	/**
+	 * This will query the scope for the given {@link EObject}s' children, then delegate to an
+	 * {@link IEObjectMatcher} to compute the Matches.
+	 * <p>
+	 * We expect at least the <code>left</code> and <code>right</code> EObjects not to be <code>null</code>.
+	 * </p>
+	 * 
+	 * @param comparison
+	 *            The comparison to which will be added detected matches.
+	 * @param scope
+	 *            The comparison scope that should be used by this engine to determine the objects to match.
+	 * @param left
+	 *            The left {@link EObject}.
+	 * @param right
+	 *            The right {@link EObject}.
+	 * @param origin
+	 *            The common ancestor of <code>left</code> and <code>right</code>.
+	 * @param monitor
+	 *            The monitor to report progress or to check for cancellation.
+	 */
+	protected void match(Comparison comparison, IComparisonScope scope, EObject left, EObject right,
+			EObject origin, Monitor monitor) {
+		if (left == null || right == null) {
+			throw new IllegalArgumentException();
+		}
+
+		final Iterator<? extends EObject> leftEObjects = Iterators.concat(Iterators.singletonIterator(left),
+				scope.getChildren(left));
+		final Iterator<? extends EObject> rightEObjects = Iterators.concat(
+				Iterators.singletonIterator(right), scope.getChildren(right));
+		final Iterator<? extends EObject> originEObjects;
+		if (origin != null) {
+			originEObjects = Iterators.concat(Iterators.singletonIterator(origin), scope.getChildren(origin));
+		} else {
+			originEObjects = Iterators.emptyIterator();
+		}
+
+		getEObjectMatcher().createMatches(comparison, leftEObjects, rightEObjects, originEObjects, monitor);
+	}
+
+	/**
+	 * This will be used to create the resource matcher that will be used by this match engine.
+	 * 
+	 * @return An {@link IResourceMatcher} that can be used to retrieve the {@link MatchResource}s for this
+	 *         comparison.
+	 */
+	protected IResourceMatcher createResourceMatcher() {
+		return new StrategyResourceMatcher();
+	}
+
+	/**
+	 * Returns the EObject matcher associated with this match engine.
+	 * 
+	 * @return The EObject matcher associated with this match engine.
+	 */
+	protected final IEObjectMatcher getEObjectMatcher() {
+		return eObjectMatcher;
+	}
+
+	/**
+	 * This will check that at least two of the three given booleans are <code>true</code>.
+	 * 
+	 * @param condition1
+	 *            First of the three booleans.
+	 * @param condition2
+	 *            Second of the three booleans.
+	 * @param condition3
+	 *            Third of the three booleans.
+	 * @return <code>true</code> if at least two of the three given booleans are <code>true</code>,
+	 *         <code>false</code> otherwise.
+	 */
+	private static boolean atLeastTwo(boolean condition1, boolean condition2, boolean condition3) {
+		// CHECKSTYLE:OFF This expression is alone in its method, and documented.
+		return condition1 && (condition2 || condition3) || (condition2 && condition3);
+		// CHECKSTYLE:ON
+	}
+
+	/**
+	 * Helper creator method that instantiate a {@link DefaultMatchEngine} that will use identifiers as
+	 * specified by the given {@code useIDs} enumeration.
+	 * 
+	 * @param useIDs
+	 *            the kinds of matcher to use.
+	 * @return a new {@link DefaultMatchEngine} instance.
+	 */
+	public static IMatchEngine create(UseIdentifiers useIDs) {
+		final IComparisonFactory comparisonFactory = new DefaultComparisonFactory(
+				new DefaultEqualityHelperFactory());
+		final IEObjectMatcher matcher = createDefaultEObjectMatcher(useIDs);
+
+		final IMatchEngine matchEngine = new DefaultMatchEngine(matcher, comparisonFactory);
+		return matchEngine;
+	}
+
+	/**
+	 * Creates and configures an {@link IEObjectMatcher} with the strategy given by {@code useIDs}. The
+	 * {@code cache} will be used to cache some expensive computation (should better a LoadingCache).
+	 * 
+	 * @param useIDs
+	 *            which strategy the return IEObjectMatcher must follow.
+	 * @return a new IEObjectMatcher.
+	 */
+	public static IEObjectMatcher createDefaultEObjectMatcher(UseIdentifiers useIDs) {
+		final IEObjectMatcher matcher;
+		final EditionDistance editionDistance = new EditionDistance();
+		switch (useIDs) {
+			case NEVER:
+				matcher = new ProximityEObjectMatcher(editionDistance);
+				break;
+			case ONLY:
+				matcher = new IdentifierEObjectMatcher();
+				break;
+			case WHEN_AVAILABLE:
+				// fall through to default
+			default:
+				// Use an ID matcher, delegating to proximity when no ID is available
+				final IEObjectMatcher contentMatcher = new ProximityEObjectMatcher(editionDistance);
+				matcher = new IdentifierEObjectMatcher(contentMatcher);
+				break;
+
+		}
+
+		return matcher;
+	}
+
+}
diff --git a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/IMatchEngine.java b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/IMatchEngine.java
index 8617c1839..6c4ff55c1 100644
--- a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/IMatchEngine.java
+++ b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/IMatchEngine.java
@@ -1,56 +1,152 @@
-/*******************************************************************************

- * Copyright (c) 2012 Obeo.

- * All rights reserved. This program and the accompanying materials

- * are made available under the terms of the Eclipse Public License v1.0

- * which accompanies this distribution, and is available at

- * http://www.eclipse.org/legal/epl-v10.html

- * 

- * Contributors:

- *     Obeo - initial API and implementation

- *******************************************************************************/

-package org.eclipse.emf.compare.match;

-

-import org.eclipse.emf.common.util.Monitor;

-import org.eclipse.emf.compare.Comparison;

-import org.eclipse.emf.compare.scope.IComparisonScope;

-

-/**

- * This class defines the general contract of a Matching engine. We expect subclasses to have a public,

- * no-argument default constructor for instantiation.

- * <p>

- * We generally expect that a call to {@link #match(IComparisonScope)} will return us every single

- * {@link org.eclipse.emf.compare.Match matches} that can be determined from the given

- * {@link IComparisonScope context}. This includes all three of :

- * <ul>

- * <li>Elements that are present on all three sides of the comparison scope,</li>

- * <li>Elements that are present on only two sides,</li>

- * <li>Elements that are only present on a single side.</li>

- * </ul>

- * </p>

- * <p>

- * Clients can subclass the {@link DefaultMatchEngine default implementation} when all that is needed is to

- * change the matching strategy.

- * </p>

- * 

- * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>

- * @see DefaultMatchEngine

- */

-public interface IMatchEngine {

-

-	/**

-	 * This is the entry point of a Comparison process. It is expected to use the provided scope in order to

-	 * determine all objects that need to be matched.

-	 * <p>

-	 * The returned Comparison should include both matched an unmatched objects. It is not the match engine's

-	 * responsibility to determine differences between objects, only to match them together.

-	 * </p>

-	 * 

-	 * @param scope

-	 *            The comparison scope that should be used by this engine to determine the objects to match.

-	 * @param monitor

-	 *            The monitor to report progress or to check for cancellation

-	 * @return An initialized {@link Comparison} model with all matches determined.

-	 */

-	Comparison match(IComparisonScope scope, Monitor monitor);

-

-}

+/*******************************************************************************
+ * Copyright (c) 2012, 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.match;
+
+import java.util.List;
+
+import org.eclipse.emf.common.util.Monitor;
+import org.eclipse.emf.compare.Comparison;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+
+/**
+ * This class defines the general contract of a Matching engine. We expect subclasses to have a public,
+ * no-argument default constructor for instantiation.
+ * <p>
+ * We generally expect that a call to {@link #match(IComparisonScope)} will return us every single
+ * {@link org.eclipse.emf.compare.Match matches} that can be determined from the given
+ * {@link IComparisonScope context}. This includes all three of :
+ * <ul>
+ * <li>Elements that are present on all three sides of the comparison scope,</li>
+ * <li>Elements that are present on only two sides,</li>
+ * <li>Elements that are only present on a single side.</li>
+ * </ul>
+ * </p>
+ * <p>
+ * Clients can subclass the {@link DefaultMatchEngine default implementation} when all that is needed is to
+ * change the matching strategy.
+ * </p>
+ * 
+ * @author <a href="mailto:laurent.goubet@obeo.fr">Laurent Goubet</a>
+ * @see DefaultMatchEngine
+ */
+public interface IMatchEngine {
+
+	/**
+	 * This is the entry point of a Comparison process. It is expected to use the provided scope in order to
+	 * determine all objects that need to be matched.
+	 * <p>
+	 * The returned Comparison should include both matched an unmatched objects. It is not the match engine's
+	 * responsibility to determine differences between objects, only to match them together.
+	 * </p>
+	 * 
+	 * @param scope
+	 *            The comparison scope that should be used by this engine to determine the objects to match.
+	 * @param monitor
+	 *            The monitor to report progress or to check for cancellation
+	 * @return An initialized {@link Comparison} model with all matches determined.
+	 */
+	Comparison match(IComparisonScope scope, Monitor monitor);
+
+	/**
+	 * Wrapper describing the given match engine.
+	 * 
+	 * @author <a href="mailto:axel.richard@obeo.fr">Axel Richard</a>
+	 * @since 3.0
+	 */
+	interface Factory {
+
+		/**
+		 * Returns the wrapped match engine.
+		 * 
+		 * @return the wrapped match engine.
+		 */
+		IMatchEngine getMatchEngine();
+
+		/**
+		 * Returns the ranking of this match engine factory.
+		 * 
+		 * @return The ranking.
+		 * @since 3.0
+		 */
+		int getRanking();
+
+		/**
+		 * Set the ranking of this match engine factory.
+		 * 
+		 * @param parseInt
+		 *            The ranking.
+		 * @since 3.0
+		 */
+		void setRanking(int parseInt);
+
+		/**
+		 * Check if the match engine factory is a good candidate for comparison.
+		 * 
+		 * @param scope
+		 *            The scope on which the match engine factory will be applied.
+		 * @return True if it is the good candidate, false otherwise.
+		 * @since 3.0
+		 */
+		boolean isMatchEngineFactoryFor(IComparisonScope scope);
+
+		/**
+		 * A registry of {@link IMatchEngine.Factory}.
+		 * 
+		 * @since 3.0
+		 */
+		interface Registry {
+
+			/**
+			 * Returns the match engine factory, for the given scope, owning the highest ranking.
+			 * 
+			 * @param scope
+			 *            The given scope.
+			 * @return The found match engine factory.
+			 */
+			IMatchEngine.Factory getHighestRankingMatchEngineFactory(IComparisonScope scope);
+
+			/**
+			 * Returns the list of {@link IMatchEngine.Factory} contained in the registry.
+			 * 
+			 * @param scope
+			 *            The scope on which the match engine factories will be applied.
+			 * @return The list of {@link IMatchEngine.Factory} contained in the registry.
+			 */
+			List<IMatchEngine.Factory> getMatchEngineFactories(IComparisonScope scope);
+
+			/**
+			 * Add to the registry the given {@link IMatchEngine.Factory}.
+			 * 
+			 * @param matchEngineFactory
+			 *            The given {@link IMatchEngine.Factory}.
+			 * @return The previous value associated with the class name of the given
+			 *         {@link IMatchEngine.Factory}, or null if there was no entry in the registry for the
+			 *         class name.
+			 */
+			IMatchEngine.Factory add(IMatchEngine.Factory matchEngineFactory);
+
+			/**
+			 * Remove from the registry the {@link IMatchEngine.Factory} designated by the given
+			 * {@link String} .
+			 * 
+			 * @param className
+			 *            The given {@link String} representing a {@link IMatchEngine.Factory}.
+			 * @return The {@link IMatchEngine.Factory} designated by the given {@link String}.
+			 */
+			IMatchEngine.Factory remove(String className);
+
+			/**
+			 * Clear the registry.
+			 */
+			void clear();
+		}
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/impl/MatchEngineFactoryImpl.java b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/impl/MatchEngineFactoryImpl.java
new file mode 100644
index 000000000..76c61c36c
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/impl/MatchEngineFactoryImpl.java
@@ -0,0 +1,105 @@
+/*******************************************************************************
+ * Copyright (c) 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.match.impl;
+
+import org.eclipse.emf.compare.match.DefaultComparisonFactory;
+import org.eclipse.emf.compare.match.DefaultEqualityHelperFactory;
+import org.eclipse.emf.compare.match.DefaultMatchEngine;
+import org.eclipse.emf.compare.match.IComparisonFactory;
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.match.eobject.IEObjectMatcher;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+import org.eclipse.emf.compare.utils.UseIdentifiers;
+
+/**
+ * The default implementation of the {@link IMatchEngine.Factory.Registry}.
+ * 
+ * @author <a href="mailto:axel.richard@obeo.fr">Axel Richard</a>
+ * @since 3.0
+ */
+public class MatchEngineFactoryImpl implements IMatchEngine.Factory {
+
+	/** The match engine created by this factory. */
+	protected IMatchEngine matchEngine;
+
+	/** Ranking of this match engine. */
+	private int ranking;
+
+	/**
+	 * Constructor that instantiate a {@link DefaultMatchEngine}.
+	 */
+	public MatchEngineFactoryImpl() {
+		this(UseIdentifiers.WHEN_AVAILABLE);
+	}
+
+	/**
+	 * Constructor that instantiate a {@link DefaultMatchEngine} that will use identifiers as specified by the
+	 * given {@code useIDs} enumeration.
+	 * 
+	 * @param useIDs
+	 *            the kinds of matcher to use.
+	 */
+	public MatchEngineFactoryImpl(UseIdentifiers useIDs) {
+		final IComparisonFactory comparisonFactory = new DefaultComparisonFactory(
+				new DefaultEqualityHelperFactory());
+		final IEObjectMatcher matcher = DefaultMatchEngine.createDefaultEObjectMatcher(useIDs);
+		matchEngine = new DefaultMatchEngine(matcher, comparisonFactory);
+	}
+
+	/**
+	 * Constructor that instantiate a {@link DefaultMatchEngine} with the given parameters.
+	 * 
+	 * @param matcher
+	 *            The matcher that will be in charge of pairing EObjects together for this comparison process.
+	 * @param comparisonFactory
+	 *            factory that will be use to instantiate Comparison as return by match() methods.
+	 */
+	public MatchEngineFactoryImpl(IEObjectMatcher matcher, IComparisonFactory comparisonFactory) {
+		matchEngine = new DefaultMatchEngine(matcher, comparisonFactory);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory#getMatchEngine()
+	 */
+	public IMatchEngine getMatchEngine() {
+		return matchEngine;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory#getRanking()
+	 */
+	public int getRanking() {
+		return ranking;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory#setRanking(int)
+	 */
+	public void setRanking(int r) {
+		ranking = r;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory#isMatchEngineFactoryFor(org.eclipse.emf.compare.scope.IComparisonScope)
+	 */
+	public boolean isMatchEngineFactoryFor(IComparisonScope scope) {
+		return true;
+	}
+
+}
diff --git a/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/impl/MatchEngineFactoryRegistryImpl.java b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/impl/MatchEngineFactoryRegistryImpl.java
new file mode 100644
index 000000000..63d35a1ed
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare/src/org/eclipse/emf/compare/match/impl/MatchEngineFactoryRegistryImpl.java
@@ -0,0 +1,151 @@
+/*******************************************************************************
+ * Copyright (c) 2013 Obeo.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ * 
+ * Contributors:
+ *     Obeo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.match.impl;
+
+import static com.google.common.collect.Iterables.filter;
+import static com.google.common.collect.Lists.newArrayList;
+
+import com.google.common.base.Preconditions;
+import com.google.common.base.Predicate;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.eclipse.emf.compare.match.IMatchEngine;
+import org.eclipse.emf.compare.scope.IComparisonScope;
+import org.eclipse.emf.compare.utils.UseIdentifiers;
+
+/**
+ * The default implementation of the {@link IMatchEngine.Factory.Registry}.
+ * 
+ * @author <a href="mailto:axel.richard@obeo.fr">Axel Richard</a>
+ * @since 3.0
+ */
+public class MatchEngineFactoryRegistryImpl implements IMatchEngine.Factory.Registry {
+
+	/** A map that associates the class name to theirs {@link IMatchEngine.Factory}. */
+	private final Map<String, IMatchEngine.Factory> map;
+
+	/**
+	 * Constructs the registry.
+	 */
+	public MatchEngineFactoryRegistryImpl() {
+		map = new ConcurrentHashMap<String, IMatchEngine.Factory>();
+	}
+
+	/**
+	 * Returns a registry filled with the default match engine factory provided by EMF Compare
+	 * {@link MatchEngineFactoryImpl}.
+	 * 
+	 * @return A registry filled with the default match engine factory provided by EMF Compare.
+	 */
+	public static IMatchEngine.Factory.Registry createStandaloneInstance() {
+		final IMatchEngine.Factory.Registry registry = new MatchEngineFactoryRegistryImpl();
+
+		final IMatchEngine.Factory matchEngineFactory = new MatchEngineFactoryImpl(
+				UseIdentifiers.WHEN_AVAILABLE);
+		matchEngineFactory.setRanking(10);
+
+		registry.add(matchEngineFactory);
+
+		return registry;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory.Registry#getHighestRankingMatchEngine(java.lang.Object)
+	 */
+	public IMatchEngine.Factory getHighestRankingMatchEngineFactory(IComparisonScope scope) {
+		Iterator<IMatchEngine.Factory> matchEngineFactories = getMatchEngineFactories(scope).iterator();
+
+		IMatchEngine.Factory ret = null;
+
+		if (matchEngineFactories.hasNext()) {
+			IMatchEngine.Factory highestRanking = matchEngineFactories.next();
+			while (matchEngineFactories.hasNext()) {
+				IMatchEngine.Factory engineFactory = matchEngineFactories.next();
+				if (engineFactory.getRanking() > highestRanking.getRanking()) {
+					highestRanking = engineFactory;
+				}
+			}
+			ret = highestRanking;
+		}
+
+		return ret;
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory.Registry#getMatchEngines(org.eclipse.emf.compare.scope.IComparisonScope)
+	 */
+	public List<IMatchEngine.Factory> getMatchEngineFactories(IComparisonScope scope) {
+		Iterable<IMatchEngine.Factory> matchEngineFactories = filter(map.values(),
+				isMatchEngineFactoryActivable(scope));
+		List<IMatchEngine.Factory> ret = newArrayList();
+		for (IMatchEngine.Factory matchEngineFactory : matchEngineFactories) {
+			ret.add(matchEngineFactory);
+		}
+		return ret;
+	}
+
+	/**
+	 * Returns a predicate that represents the activation condition based on the scope.
+	 * 
+	 * @param scope
+	 *            The scope on which the group provider will be applied.
+	 * @return A predicate that represents the activation condition based on the scope.
+	 */
+	private static Predicate<IMatchEngine.Factory> isMatchEngineFactoryActivable(final IComparisonScope scope) {
+		return new Predicate<IMatchEngine.Factory>() {
+			/**
+			 * {@inheritDoc}
+			 * 
+			 * @see com.google.common.base.Predicate#apply(java.lang.Object)
+			 */
+			public boolean apply(IMatchEngine.Factory factory) {
+				return factory.isMatchEngineFactoryFor(scope);
+			}
+		};
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory.Registry#add(org.eclipse.emf.compare.match.IMatchEngine)
+	 */
+	public IMatchEngine.Factory add(IMatchEngine.Factory filter) {
+		Preconditions.checkNotNull(filter);
+		return map.put(filter.getClass().getName(), filter);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory.Registry#remove(java.lang.String)
+	 */
+	public IMatchEngine.Factory remove(String className) {
+		return map.remove(className);
+	}
+
+	/**
+	 * {@inheritDoc}
+	 * 
+	 * @see org.eclipse.emf.compare.match.IMatchEngine.Factory.Registry#clear()
+	 */
+	public void clear() {
+		map.clear();
+	}
+
+}