[466607] Enhance EMFModelProvider to consider multiple resources at once

The EMFModelProvider now overrides the getMappings(Resource[] ...)
method to allow for optimized results.

Depending on the EMF Compare resolution settings the logical model can
not be computed as a whole when only looking at single resources. The
getMappings(Resource[] ...) method now uses the already available
multi-resource input to combine overlapping logical models to a single
model.

Since the EMFModelProvider is for example used during merging, the
optimized results avoid redundant comparisons and mergings and therefore
save time and computation power.

Includes testcases.

Bug: 466607
Signed-off-by: Stefan Dirix <sdirix@eclipsesource.com>
Change-Id: Id928bc1a05e353bf2b721243c264d09de07eebc3

13 files changed, 815 insertions, 44 deletions

diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/EMFModelProviderTest.java b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/EMFModelProviderTest.java
new file mode 100644
index 000000000..ae9d08354
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/EMFModelProviderTest.java
@@ -0,0 +1,523 @@
+/*******************************************************************************
+ * Copyright (c) 2015 EclipseSource Muenchen GmbH and others.
+ * 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:
+ *     Stefan Dirix - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.emf.compare.ide.ui.tests.logical.modelprovider;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.eclipse.core.resources.IContainer;
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IProject;
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.resources.IStorage;
+import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.resources.mapping.IModelProviderDescriptor;
+import org.eclipse.core.resources.mapping.ModelProvider;
+import org.eclipse.core.resources.mapping.RemoteResourceMappingContext;
+import org.eclipse.core.resources.mapping.ResourceMapping;
+import org.eclipse.core.resources.mapping.ResourceTraversal;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.FileLocator;
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.NullProgressMonitor;
+import org.eclipse.core.runtime.Platform;
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.compare.ide.ui.internal.EMFCompareIDEUIPlugin;
+import org.eclipse.emf.compare.ide.ui.internal.logical.EMFModelProvider;
+import org.eclipse.emf.compare.ide.ui.internal.logical.resolver.CrossReferenceResolutionScope;
+import org.eclipse.emf.compare.ide.ui.internal.preferences.EMFCompareUIPreferences;
+import org.eclipse.emf.compare.ide.ui.tests.CompareTestCase;
+import org.eclipse.emf.compare.ide.ui.tests.workspace.TestProject;
+import org.eclipse.jface.preference.IPreferenceStore;
+import org.junit.AfterClass;
+import org.junit.Test;
+import org.osgi.framework.Bundle;
+
+/**
+ * Tests the EMFModelProvider to return a minimum number of {@link ResourceMapping}s in cases where it is not
+ * straightforward (e.g. resolution scope set to "workspace") but still doable since it has all required input
+ * resources.
+ * 
+ * @author Stefan Dirix <sdirix@eclipsesource.com>
+ */
+@SuppressWarnings({"nls", "restriction" })
+public class EMFModelProviderTest extends CompareTestCase {
+
+	/**
+	 * Path to the test data.
+	 */
+	private static final String TEST_DATA_PATH = "src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/";
+
+	/**
+	 * The bundle containing this test.
+	 */
+	private static final String TEST_BUNDLE = "org.eclipse.emf.compare.ide.ui.tests";
+
+	/**
+	 * Name of test project 1.
+	 */
+	private static final String PROJECT_NAME_1 = "project1";
+
+	/**
+	 * Name of test project 2.
+	 */
+	private static final String PROJECT_NAME_2 = "project2";
+
+	/**
+	 * Name of test project 3.
+	 */
+	private static final String PROJECT_NAME_3 = "project3";
+
+	/**
+	 * Reset the resolution scope preference.
+	 */
+	@AfterClass
+	public static void setDefaultResolutionScope() {
+		final IPreferenceStore store = EMFCompareIDEUIPlugin.getDefault().getPreferenceStore();
+		store.setToDefault(EMFCompareUIPreferences.RESOLUTION_SCOPE_PREFERENCE);
+	}
+
+	/**
+	 * Delete created projects.
+	 */
+	@AfterClass
+	public static void deleteProjects() throws CoreException {
+		deleteProject(PROJECT_NAME_1);
+		deleteProject(PROJECT_NAME_2);
+		deleteProject(PROJECT_NAME_3);
+	}
+
+	/**
+	 * Deletes the project wit the given {@code name}.
+	 * 
+	 * @param name
+	 *            The name of the project which shall be deleted.
+	 */
+	private static void deleteProject(String name) throws CoreException {
+		final IProject project = new TestProject(name).getProject();
+		project.delete(true, true, new NullProgressMonitor());
+	}
+
+	/**
+	 * Sets the resolution scope to the given preference.
+	 * 
+	 * @param preference
+	 *            The value to which the resolution scope preference is set.
+	 */
+	private void setResolutionScope(String preference) {
+		final IPreferenceStore store = EMFCompareIDEUIPlugin.getDefault().getPreferenceStore();
+		store.setValue(EMFCompareUIPreferences.RESOLUTION_SCOPE_PREFERENCE, preference);
+	}
+
+	/**
+	 * Creates the projects and test files for case1.
+	 * 
+	 * @return The created test files.
+	 */
+	private IFile[] createProjectFilesCase1() throws CoreException, IOException, URISyntaxException {
+		IProject project1 = new TestProject(PROJECT_NAME_1).getProject();
+		IProject project2 = new TestProject(PROJECT_NAME_2).getProject();
+		IProject project3 = new TestProject(PROJECT_NAME_3).getProject();
+		IFile file1 = addToProject(project1, "case1/file1.ecore", "");
+		IFile file2 = addToProject(project2, "case1/file2.ecore", "");
+		IFile file3 = addToProject(project3, "case1/file3.ecore", "");
+		return new IFile[] {file1, file2, file3 };
+	}
+
+	/**
+	 * Creates the projects and test files for case2.
+	 * 
+	 * @return The created test files.
+	 */
+	private IFile[] createProjectFilesCase2() throws CoreException, IOException, URISyntaxException {
+		IProject project1 = new TestProject(PROJECT_NAME_1).getProject();
+		IProject project2 = new TestProject(PROJECT_NAME_2).getProject();
+		IProject project3 = new TestProject(PROJECT_NAME_3).getProject();
+		IFile file1 = addToProject(project1, "case2/file1.ecore", "");
+		IFile file2 = addToProject(project2, "case2/file2.ecore", "");
+		IFile file3 = addToProject(project3, "case2/file3.ecore", "");
+		return new IFile[] {file1, file2, file3 };
+	}
+
+	/**
+	 * Creates the projects and test files for case3.
+	 * 
+	 * @return The created test files.
+	 */
+	private IFile[] createProjectFilesCase3() throws CoreException, IOException, URISyntaxException {
+		IProject project1 = new TestProject(PROJECT_NAME_1).getProject();
+		IFile file1 = addToProject(project1, "case3/file1.ecore", "");
+		IFile file2 = addToProject(project1, "case3/file2.ecore", "/a/");
+		IFile file3 = addToProject(project1, "case3/file3.ecore", "/a/");
+		return new IFile[] {file1, file2, file3 };
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row:
+	 * {@code project1/file1 -> project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#OUTGOING}.
+	 */
+	@Test
+	public void testResourceMappingCase1_Outgoing() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.OUTGOING.toString());
+		final IFile[] files = createProjectFilesCase1();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}, {file2,file3}, {file3}
+		assertEquals(3, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can optimize to {file1,file2,file3}
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row:
+	 * {@code project1/file1 -> project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#CONTAINER}.
+	 */
+	@Test
+	public void testResourceMappingCase1_Container() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.CONTAINER.toString());
+		final IFile[] files = createProjectFilesCase1();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1}, {file2}, {file3}
+		assertEquals(3, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can not optimize and returns the same
+		assertEquals(3, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row:
+	 * {@code project1/file1 -> project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#PROJECT}.
+	 */
+	@Test
+	public void testResourceMappingCase1_Project() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.PROJECT.toString());
+		final IFile[] files = createProjectFilesCase1();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1}, {file2}, {file3}
+		assertEquals(3, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can not optimize and returns the same
+		assertEquals(3, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row:
+	 * {@code project1/file1 -> project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#WORKSPACE}.
+	 */
+	@Test
+	public void testResourceMappingCase1_Workspace() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.WORKSPACE.toString());
+		final IFile[] files = createProjectFilesCase1();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}
+		assertEquals(1, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// The mapping can not be optimized further
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements fork: {@code project1/file1 -> project3/file3} &
+	 * {@code project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#OUTGOING}.
+	 */
+	@Test
+	public void testResourceMappingCase2_Outgoing() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.OUTGOING.toString());
+		final IFile[] files = createProjectFilesCase2();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}, {file3}
+		assertEquals(2, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can optimize to {file1,file2,file3}
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements fork: {@code project1/file1 -> project3/file3} &
+	 * {@code project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#CONTAINER}.
+	 */
+	@Test
+	public void testResourceMappingCase2_Container() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.CONTAINER.toString());
+		final IFile[] files = createProjectFilesCase2();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1}, {file2}, {file3}
+		assertEquals(3, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can not optimize and returns the same
+		assertEquals(3, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements fork: {@code project1/file1 -> project3/file3} &
+	 * {@code project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#PROJECT}.
+	 */
+	@Test
+	public void testResourceMappingCase2_Project() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.PROJECT.toString());
+		final IFile[] files = createProjectFilesCase2();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1}, {file2}, {file3}
+		assertEquals(3, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can not optimize and returns the same
+		assertEquals(3, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements fork: {@code project1/file1 -> project3/file3} &
+	 * {@code project2/file2 -> project3/file3} and resolution scope
+	 * {@link CrossReferenceResolutionScope#WORKSPACE}.
+	 */
+	@Test
+	public void testResourceMappingCase2_Workspace() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.WORKSPACE.toString());
+		final IFile[] files = createProjectFilesCase2();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}
+		assertEquals(1, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// The mapping can not be optimized further
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row: {@code file1 -> a/file2 -> a/file3} and resolution
+	 * scope {@link CrossReferenceResolutionScope#OUTGOING}.
+	 */
+	@Test
+	public void testResourceMappingCase3_Outgoing() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.OUTGOING.toString());
+		final IFile[] files = createProjectFilesCase3();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}, {file2,file3}, {file3}
+		assertEquals(3, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can optimize to {file1,file2,file3}
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row: {@code file1 -> a/file2 -> a/file3} and resolution
+	 * scope {@link CrossReferenceResolutionScope#CONTAINER}.
+	 */
+	@Test
+	public void testResourceMappingCase3_Container() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.CONTAINER.toString());
+		final IFile[] files = createProjectFilesCase3();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1}, {file2,file3}
+		assertEquals(2, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// EMFModelProvider can optimize to {file1,file2,file3}
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row: {@code file1 -> a/file2 -> a/file3} and resolution
+	 * scope {@link CrossReferenceResolutionScope#PROJECT}.
+	 */
+	@Test
+	public void testResourceMappingCase3_Project() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.PROJECT.toString());
+		final IFile[] files = createProjectFilesCase3();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}
+		assertEquals(1, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// The mapping can not be optimized further
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Tests the EMFModelProvider with a requirements row: {@code file1 -> a/file2 -> a/file3} and resolution
+	 * scope {@link CrossReferenceResolutionScope#WORKSPACE}.
+	 */
+	@Test
+	public void testResourceMappingCase3_Workspace() throws CoreException, IOException, URISyntaxException {
+		setResolutionScope(CrossReferenceResolutionScope.WORKSPACE.toString());
+		final IFile[] files = createProjectFilesCase3();
+
+		final ResourceMapping[] singleResourceMappings = collectSingleResourceMappings(files);
+		// {file1,file2,file3}
+		assertEquals(1, singleResourceMappings.length);
+
+		final ResourceMapping[] combinedResourceMappings = getCombinedResourceMappings(files);
+		// The mapping can not be optimized further
+		assertEquals(1, combinedResourceMappings.length);
+	}
+
+	/**
+	 * Collects all resource mappings of the given files by calling
+	 * {@link EMFModelProvider#getMappings(IResource, org.eclipse.core.resources.mapping.ResourceMappingContext, IProgressMonitor)}
+	 * on each of them and combining the results. This is how the default implementation within the
+	 * ModelProvider class is implemented.
+	 * 
+	 * @param files
+	 *            The files for which the resource mappings shall be calculated.
+	 * @return The combined result of determining the resource mapping for each given file separately.
+	 */
+	private ResourceMapping[] collectSingleResourceMappings(IFile... files) throws CoreException {
+		final EMFModelProvider emfModelProvider = getEMFModelProvider();
+		Set<ResourceMapping> mappings = new HashSet<ResourceMapping>();
+		for (int i = 0; i < files.length; i++) {
+			IResource resource = files[i];
+			ResourceMapping[] resourceMappings = emfModelProvider.getMappings(resource, new StubContext(),
+					new NullProgressMonitor());
+			if (resourceMappings.length > 0) {
+				mappings.addAll(Arrays.asList(resourceMappings));
+			}
+		}
+		return mappings.toArray(new ResourceMapping[mappings.size()]);
+	}
+
+	/**
+	 * Returns the result of calling
+	 * {@link EMFModelProvider#getTraversals(ResourceMapping[], org.eclipse.core.resources.mapping.ResourceMappingContext, IProgressMonitor)}
+	 * to determine the ResourceMappings.
+	 * 
+	 * @param files
+	 *            The files for which the resource mappings shall be determined.
+	 * @return The resource mappings for the given file when {@link EMFModelProvider} is given a chance to
+	 *         optimize.
+	 */
+	private ResourceMapping[] getCombinedResourceMappings(IFile... files) throws CoreException {
+		final EMFModelProvider emfModelProvider = getEMFModelProvider();
+		return emfModelProvider.getMappings(files, new StubContext(), new NullProgressMonitor());
+	}
+
+	private EMFModelProvider getEMFModelProvider() throws CoreException {
+		final IModelProviderDescriptor[] descriptors = ModelProvider.getModelProviderDescriptors();
+		for (IModelProviderDescriptor descriptor : descriptors) {
+			if (descriptor.getModelProvider() instanceof EMFModelProvider) {
+				return (EMFModelProvider)descriptor.getModelProvider();
+			}
+		}
+		return null;
+	}
+
+	/**
+	 * Copies the file located in {@link #TEST_DATA_PATH} + {@code filePath} to the given
+	 * {@code destinationPath} in {@code iProject}.
+	 * 
+	 * @param iProject
+	 *            The {@link IProject} to which the file is added.
+	 * @param filePath
+	 *            The path relative to {@link #TEST_DATA_PATH} where the file is originally located.
+	 * @param destinationPath
+	 *            The path in the {@code iProject} to which the file will be copied.
+	 * @return The newly created {@link IFile}.
+	 */
+	private IFile addToProject(IProject iProject, String filePath, String destinationPath)
+			throws IOException, URISyntaxException, CoreException {
+		final Bundle bundle = Platform.getBundle(TEST_BUNDLE);
+		final URI fileUri = getFileUri(bundle.getEntry(TEST_DATA_PATH + filePath));
+
+		final File file = project.getOrCreateFile(iProject, destinationPath + fileUri.lastSegment());
+
+		copyFile(toFile(fileUri), file);
+
+		return project.getIFile(iProject, file);
+	}
+
+	private URI getFileUri(final URL bundleUrl) throws IOException {
+		URL fileLocation = FileLocator.toFileURL(bundleUrl);
+		return URI.createFileURI(fileLocation.getPath());
+	}
+
+	private File toFile(final URI fileUri) throws URISyntaxException {
+		return new File(fileUri.toFileString());
+	}
+
+	/**
+	 * Stub for a {@link RemoteResourceMappingContext}. The class is used to trigger the creation of a proper
+	 * comparison scope within the {@link EMFModelProvider}.
+	 */
+	private class StubContext extends RemoteResourceMappingContext {
+
+		@Override
+		public IStorage fetchBaseContents(IFile file, IProgressMonitor monitor) throws CoreException {
+			return null;
+		}
+
+		@Override
+		public IResource[] fetchMembers(IContainer container, IProgressMonitor monitor) throws CoreException {
+			return new IResource[0];
+		}
+
+		@Override
+		public IStorage fetchRemoteContents(IFile file, IProgressMonitor monitor) throws CoreException {
+			return null;
+		}
+
+		@Override
+		public IProject[] getProjects() {
+			return ResourcesPlugin.getWorkspace().getRoot().getProjects();
+		}
+
+		@Override
+		public boolean hasLocalChange(IResource resource, IProgressMonitor monitor) throws CoreException {
+			return true;
+		}
+
+		@Override
+		public boolean hasRemoteChange(IResource resource, IProgressMonitor monitor) throws CoreException {
+			return true;
+		}
+
+		@Override
+		public boolean isThreeWay() {
+			return false;
+		}
+
+		@Override
+		public void refresh(ResourceTraversal[] traversals, int flags, IProgressMonitor monitor)
+				throws CoreException {
+		}
+
+	}
+}
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file1.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file1.ecore
new file mode 100644
index 000000000..fdc0ea7cb
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file1.ecore
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
+    xmi:id="_A" name="File1_A">
+  <eSubpackages href="../project2/file2.ecore#_B"/>
+</ecore:EPackage>
\ No newline at end of file
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file2.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file2.ecore
new file mode 100644
index 000000000..537d7623e
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file2.ecore
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
+    xmi:id="_B" name="File2_B">
+  <eSubpackages href="../project3/file3.ecore#_C"/>
+</ecore:EPackage>
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file3.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file3.ecore
new file mode 100644
index 000000000..07e473eeb
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case1/file3.ecore
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" xmi:id="_C" name="File3_C">
+</ecore:EPackage>
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file1.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file1.ecore
new file mode 100644
index 000000000..373b2df6e
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file1.ecore
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
+    xmi:id="_A" name="File1_A">
+  <eSubpackages href="../project3/file3.ecore#_C"/>
+</ecore:EPackage>
\ No newline at end of file
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file2.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file2.ecore
new file mode 100644
index 000000000..537d7623e
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file2.ecore
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
+    xmi:id="_B" name="File2_B">
+  <eSubpackages href="../project3/file3.ecore#_C"/>
+</ecore:EPackage>
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file3.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file3.ecore
new file mode 100644
index 000000000..07e473eeb
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case2/file3.ecore
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" xmi:id="_C" name="File3_C">
+</ecore:EPackage>
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file1.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file1.ecore
new file mode 100644
index 000000000..a21e37c62
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file1.ecore
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
+    xmi:id="_A" name="File1_A">
+  <eSubpackages href="a/file2.ecore#_B"/>
+</ecore:EPackage>
\ No newline at end of file
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file2.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file2.ecore
new file mode 100644
index 000000000..531c77313
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file2.ecore
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
+    xmi:id="_B" name="File2_B">
+  <eSubpackages href="file3.ecore#_C"/>
+</ecore:EPackage>
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file3.ecore b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file3.ecore
new file mode 100644
index 000000000..07e473eeb
--- /dev/null
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/logical/modelprovider/data/case3/file3.ecore
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ecore:EPackage xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" xmi:id="_C" name="File3_C">
+</ecore:EPackage>
diff --git a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/suite/AllTests.java b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/suite/AllTests.java
index 81deaa288..d8c01aea8 100644
--- a/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/suite/AllTests.java
+++ b/plugins/org.eclipse.emf.compare.ide.ui.tests/src/org/eclipse/emf/compare/ide/ui/tests/suite/AllTests.java
@@ -8,6 +8,7 @@
  * Contributors:
  *     Obeo - initial API and implementation
  *     Philip Langer - adds test classes
+ *     Stefan Dirix - add EMFModelProviderTest
  *******************************************************************************/
 package org.eclipse.emf.compare.ide.ui.tests.suite;
 
@@ -18,6 +19,7 @@ import junit.textui.TestRunner;
 import org.eclipse.emf.compare.ComparePackage;
 import org.eclipse.emf.compare.ide.ui.tests.compareconfiguration.EMFCompareConfigurationTest;
 import org.eclipse.emf.compare.ide.ui.tests.contentmergeviewer.notloadedfragment.NotLoadedFragmentItemTest;
+import org.eclipse.emf.compare.ide.ui.tests.logical.modelprovider.EMFModelProviderTest;
 import org.eclipse.emf.compare.ide.ui.tests.logical.resolver.DependencyGraphUpdaterTest;
 import org.eclipse.emf.compare.ide.ui.tests.logical.resolver.GraphResolutionTest;
 import org.eclipse.emf.compare.ide.ui.tests.logical.resolver.ResolutionEventsTest;
@@ -39,19 +41,12 @@ import org.junit.runners.Suite;
 import org.junit.runners.Suite.SuiteClasses;
 
 @RunWith(Suite.class)
-@SuiteClasses({EMFCompareConfigurationTest.class,
-		DependenciesTest.class,
-		MergeActionTest.class,
-		PseudoConflictsMergeActionTest.class,
-		BugsTestSuite.class,
-		NavigatableTest.class,
-		NotLoadedFragmentNodeTest.class,
-		NotLoadedFragmentItemTest.class,
-		ResolutionEventsTest.class,
-		ResourceComputationSchedulerTest.class,
-		ThreadedModelResolverGraphTest.class,
-		ThreadedModelResolverWithCustomDependencyProviderTest.class,
-		DependencyGraphUpdaterTest.class, GraphResolutionTest.class })
+@SuiteClasses({EMFCompareConfigurationTest.class, DependenciesTest.class, MergeActionTest.class,
+		PseudoConflictsMergeActionTest.class, BugsTestSuite.class, NavigatableTest.class,
+		NotLoadedFragmentNodeTest.class, NotLoadedFragmentItemTest.class, ResolutionEventsTest.class,
+		ResourceComputationSchedulerTest.class, ThreadedModelResolverGraphTest.class,
+		ThreadedModelResolverWithCustomDependencyProviderTest.class, DependencyGraphUpdaterTest.class,
+		GraphResolutionTest.class, EMFModelProviderTest.class })
 public class AllTests {
 	/**
 	 * Launches the test with the given arguments.
diff --git a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/ComparisonScopeBuilder.java b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/ComparisonScopeBuilder.java
index bb2850367..0bad985bb 100644
--- a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/ComparisonScopeBuilder.java
+++ b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/ComparisonScopeBuilder.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2013, 2015 Obeo.
+ * Copyright (c) 2013, 2015 Obeo and others.
  * 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
@@ -7,6 +7,7 @@
  * 
  * Contributors:
  *     Obeo - initial API and implementation
+ *     Stefan Dirix - bug 466607
  *******************************************************************************/
 package org.eclipse.emf.compare.ide.ui.internal.logical;
 
@@ -184,41 +185,36 @@ public final class ComparisonScopeBuilder {
 	 *            one. Can be <code>null</code>.
 	 * @param monitor
 	 *            The monitor on which to report progress information to the user.
-	 * @return The newly created SynchronizationModel, <code>null</code> in case of user interruption.
+	 * @return The newly created SynchronizationModel.
+	 * @throws InterruptedException
+	 *             In case of user interruption.
 	 */
 	/* package */SynchronizationModel buildSynchronizationModel(ITypedElement left, ITypedElement right,
-			ITypedElement origin, IProgressMonitor monitor) {
+			ITypedElement origin, IProgressMonitor monitor) throws InterruptedException {
 		if (LOGGER.isDebugEnabled()) {
 			LOGGER.debug("buildSynchronizationModel - START"); //$NON-NLS-1$
 		}
 		SubMonitor subMonitor = SubMonitor.convert(monitor, 100);
 		subMonitor.subTask(EMFCompareIDEUIMessages.getString("EMFSynchronizationModel.resolving")); //$NON-NLS-1$
-		try {
-			final SynchronizationModel syncModel;
-			if (LOGGER.isDebugEnabled()) {
-				LOGGER.debug("buildSynchronizationModel - Creating sync model"); //$NON-NLS-1$
-			}
-			if (storageAccessor != null) {
-				syncModel = createSynchronizationModel(storageAccessor, left, right, origin, subMonitor
-						.newChild(90));
-			} else {
-				syncModel = createSynchronizationModel(left, right, origin, subMonitor.newChild(90));
-			}
-			if (LOGGER.isDebugEnabled()) {
-				LOGGER.debug("buildSynchronizationModel - Minimizing model"); //$NON-NLS-1$
-			}
-			minimizer.minimize(syncModel, subMonitor.newChild(10));
-			if (LOGGER.isDebugEnabled()) {
-				LOGGER.debug("buildSynchronizationModel - FINISH NORMALLY"); //$NON-NLS-1$
-			}
-			return syncModel;
-		} catch (InterruptedException e) {
-			Thread.currentThread().interrupt();
-			if (LOGGER.isDebugEnabled()) {
-				LOGGER.debug("buildSynchronizationModel - FINISH ABNORMALLY"); //$NON-NLS-1$
-			}
-			return null;
+
+		final SynchronizationModel syncModel;
+		if (LOGGER.isDebugEnabled()) {
+			LOGGER.debug("buildSynchronizationModel - Creating sync model"); //$NON-NLS-1$
+		}
+		if (storageAccessor != null) {
+			syncModel = createSynchronizationModel(storageAccessor, left, right, origin, subMonitor
+					.newChild(90));
+		} else {
+			syncModel = createSynchronizationModel(left, right, origin, subMonitor.newChild(90));
+		}
+		if (LOGGER.isDebugEnabled()) {
+			LOGGER.debug("buildSynchronizationModel - Minimizing model"); //$NON-NLS-1$
+		}
+		minimizer.minimize(syncModel, subMonitor.newChild(10));
+		if (LOGGER.isDebugEnabled()) {
+			LOGGER.debug("buildSynchronizationModel - FINISH NORMALLY"); //$NON-NLS-1$
 		}
+		return syncModel;
 	}
 
 	/**
diff --git a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/EMFModelProvider.java b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/EMFModelProvider.java
index bcde040fd..441098895 100644
--- a/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/EMFModelProvider.java
+++ b/plugins/org.eclipse.emf.compare.ide.ui/src/org/eclipse/emf/compare/ide/ui/internal/logical/EMFModelProvider.java
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2012, 2015 Obeo.
+ * Copyright (c) 2012, 2015 Obeo and others.
  * 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
@@ -7,15 +7,27 @@
  * 
  * Contributors:
  *     Obeo - initial API and implementation
+ *     Stefan Dirix - bug 466607
  *******************************************************************************/
 package org.eclipse.emf.compare.ide.ui.internal.logical;
 
+import com.google.common.base.Joiner;
 import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
 import com.google.common.cache.CacheLoader;
 import com.google.common.cache.LoadingCache;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 
 import org.apache.log4j.Logger;
@@ -32,6 +44,8 @@ import org.eclipse.core.runtime.IAdaptable;
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.emf.compare.ide.ui.internal.EMFCompareIDEUIPlugin;
+import org.eclipse.emf.compare.ide.ui.internal.logical.resolver.CrossReferenceResolutionScope;
+import org.eclipse.emf.compare.ide.ui.internal.logical.resolver.ResolutionUtil;
 import org.eclipse.emf.compare.ide.ui.logical.IModelMinimizer;
 import org.eclipse.emf.compare.ide.ui.logical.IModelResolver;
 import org.eclipse.emf.compare.ide.ui.logical.IStorageProvider;
@@ -132,6 +146,62 @@ public class EMFModelProvider extends ModelProvider {
 		return super.getMappings(resource, context, monitor);
 	}
 
+	@Override
+	public ResourceMapping[] getMappings(IResource[] resources, ResourceMappingContext context,
+			IProgressMonitor monitor) throws CoreException {
+		if (LOGGER.isInfoEnabled()) {
+			final Joiner joiner = Joiner.on(",").skipNulls(); //$NON-NLS-1$
+			final String resourceList = joiner.join(resources);
+			LOGGER.info("getMappings() - START for " + resourceList); //$NON-NLS-1$
+		}
+
+		final List<ResourceMapping> mappings = new ArrayList<ResourceMapping>();
+
+		// collect all IFiles
+		final List<IFile> files = new ArrayList<IFile>();
+		final List<IResource> remainingResources = new ArrayList<IResource>();
+
+		for (IResource resource : resources) {
+			if (resource instanceof IFile) {
+				files.add((IFile)resource);
+			} else {
+				remainingResources.add(resource);
+			}
+		}
+
+		try {
+			final Map<SynchronizationModel, IFile> syncModels = computeLogicalModels(files, context, monitor);
+			for (Map.Entry<SynchronizationModel, IFile> entry : syncModels.entrySet()) {
+				final ResourceMapping mapping = new EMFResourceMapping(entry.getValue(), context, entry
+						.getKey(), PROVIDER_ID);
+				mappings.add(mapping);
+			}
+
+		} catch (InterruptedException e) {
+			Thread.currentThread().interrupt();
+			if (LOGGER.isInfoEnabled()) {
+				LOGGER.info("getMappings() - interrupt exception: fallback to super."); //$NON-NLS-1$
+			}
+			return super.getMappings(resources, context, monitor);
+		}
+
+		if (!remainingResources.isEmpty()) {
+			if (LOGGER.isInfoEnabled()) {
+				final Joiner joiner = Joiner.on(",").skipNulls(); //$NON-NLS-1$
+				final String resourceList = joiner.join(remainingResources);
+				LOGGER.info("getMappings() - not all resources were handled. fallback to super for: " + resourceList); //$NON-NLS-1$
+			}
+			mappings.addAll(Arrays.asList(super.getMappings(remainingResources
+					.toArray(new IResource[remainingResources.size()]), context, monitor)));
+		} else {
+			if (LOGGER.isInfoEnabled()) {
+				LOGGER.info("getMappings() - FINISH NORMALLY"); //$NON-NLS-1$
+			}
+		}
+
+		return mappings.toArray(new ResourceMapping[mappings.size()]);
+	}
+
 	/**
 	 * Clears the caches of this provider.
 	 */
@@ -182,8 +252,13 @@ public class EMFModelProvider extends ModelProvider {
 				}
 				syncModel = computeLogicalModel(file, context, monitor);
 				if (syncModel != null) {
-					for (IResource res : syncModel.getResources()) {
-						resourceMappingCache.put(res, syncModel);
+					if (ResolutionUtil.getResolutionScope().equals(CrossReferenceResolutionScope.WORKSPACE)) {
+						// logical model will be the same for all resources contained in the model
+						for (IResource res : syncModel.getResources()) {
+							resourceMappingCache.put(res, syncModel);
+						}
+					} else {
+						resourceMappingCache.put(file, syncModel);
 					}
 				}
 			} else if (LOGGER.isDebugEnabled()) {
@@ -274,6 +349,146 @@ public class EMFModelProvider extends ModelProvider {
 	}
 
 	/**
+	 * Resolve the logical model(s) of the given files.
+	 * <p>
+	 * When model resolution setting is not set to "workspace" the
+	 * {@link #computeLogicalModel(IFile, ResourceMappingContext, IProgressMonitor)} method can not guarantee
+	 * to compute the whole logical model for the given file. But there are actually use cases in which the
+	 * client already knows which files constitute the logical model, see for example
+	 * {@link #getMappings(IResource[], ResourceMappingContext, IProgressMonitor)}.
+	 * </p>
+	 * <p>
+	 * This method tries to combine the logical models of the given {@code files} if applicable. Depending of
+	 * the given {@code files} the whole logical model may be resolved independent of the workspace resolution
+	 * settings.
+	 * </p>
+	 *
+	 * @param files
+	 *            The {@link IFile}s for which the logical model(s) is to be computed.
+	 * @param context
+	 *            The resource mapping context.
+	 * @param monitor
+	 *            Used to display progress information to the user.
+	 * @return The computed logical models each mapped to the first file from which they were resolved. The
+	 *         logical models are disjoint.
+	 * @throws CoreException
+	 *             If we cannot retrieve the content of a resource for some reason.
+	 * @throws InterruptedException
+	 *             If the user interrupts the resolving.
+	 */
+	Map<SynchronizationModel, IFile> computeLogicalModels(Collection<IFile> files,
+			ResourceMappingContext context, IProgressMonitor monitor) throws CoreException,
+			InterruptedException {
+		if (LOGGER.isDebugEnabled()) {
+			final Joiner joiner = Joiner.on(",").skipNulls(); //$NON-NLS-1$
+			final String fileList = joiner.join(files);
+			LOGGER.debug("computeLogicalModels() - START with " + fileList); //$NON-NLS-1$
+		}
+		final Map<SynchronizationModel, IFile> syncModels = new LinkedHashMap<SynchronizationModel, IFile>();
+
+		for (IFile file : files) {
+			final SynchronizationModel currentSyncModel = getOrComputeLogicalModel(file, context, monitor);
+
+			if (currentSyncModel == null) {
+				// skip file
+				if (LOGGER.isDebugEnabled()) {
+					LOGGER.debug("computeLogicalModels() - Could not determine logical model for \"" + file + "\". SKIP file."); //$NON-NLS-1$ //$NON-NLS-2$
+				}
+				continue;
+			}
+
+			// subsets can be shortcutted
+			boolean combineModels = false;
+
+			final List<SynchronizationModel> toCombine = new LinkedList<SynchronizationModel>();
+
+			for (SynchronizationModel syncModel : syncModels.keySet()) {
+
+				if (!Collections.disjoint(syncModel.getResources(), currentSyncModel.getResources())) {
+					toCombine.add(syncModel);
+
+					if (!syncModel.getResources().containsAll(currentSyncModel.getResources())) {
+						// the model is not a subset -> deactivate shortcut
+						combineModels = true;
+					}
+				}
+			}
+
+			// if there are no models to combine, add this model to the result set
+			if (toCombine.isEmpty()) {
+				syncModels.put(currentSyncModel, file);
+			}
+
+			// when a model can be added to multiple other models, all these models must be combined
+			if (combineModels) {
+				final Iterator<SynchronizationModel> it = toCombine.iterator();
+				final SynchronizationModel firstToCombine = it.next();
+				final IFile value = syncModels.get(firstToCombine);
+
+				SynchronizationModel combinedModel = combineModels(currentSyncModel, firstToCombine);
+				syncModels.remove(firstToCombine);
+
+				while (it.hasNext()) {
+					final SynchronizationModel currentModel = it.next();
+					combinedModel = combineModels(combinedModel, currentModel);
+					syncModels.remove(currentModel);
+				}
+
+				syncModels.put(combinedModel, value);
+			}
+		}
+
+		if (LOGGER.isDebugEnabled()) {
+			LOGGER.debug("computeLogicalModels() - FINISH with " + syncModels.size() + " models"); //$NON-NLS-1$ //$NON-NLS-2$
+		}
+		return syncModels;
+	}
+
+	/**
+	 * Combines the given {@link SynchronizationModel}s to a new model.
+	 *
+	 * @param modelA
+	 *            The model to combine.
+	 * @param modelB
+	 *            The model to combine.
+	 * @return A new {@link SynchronizationModel} which contains the combination of {@link StorageTraversal}s
+	 *         of the given models.
+	 */
+	private SynchronizationModel combineModels(SynchronizationModel modelA, SynchronizationModel modelB) {
+		Set<IStorage> left = new HashSet<IStorage>();
+		Set<IStorage> right = new HashSet<IStorage>();
+		Set<IStorage> origin = new HashSet<IStorage>();
+
+		StorageTraversal leftTraversal = null;
+		StorageTraversal rightTraversal = null;
+		StorageTraversal originTraversal = null;
+
+		if (modelA.getLeftTraversal() != null) {
+			left.addAll(modelA.getLeftTraversal().getStorages());
+			if (modelB != null && modelB.getLeftTraversal() != null) {
+				left.addAll(modelB.getLeftTraversal().getStorages());
+			}
+			leftTraversal = new StorageTraversal(left);
+		}
+		if (modelA.getRightTraversal() != null) {
+			right.addAll(modelA.getRightTraversal().getStorages());
+			if (modelB != null && modelB.getRightTraversal() != null) {
+				right.addAll(modelB.getRightTraversal().getStorages());
+			}
+			rightTraversal = new StorageTraversal(right);
+		}
+		if (modelA.getOriginTraversal() != null) {
+			origin.addAll(modelA.getOriginTraversal().getStorages());
+			if (modelB != null && modelB.getOriginTraversal() != null) {
+				right.addAll(modelB.getOriginTraversal().getStorages());
+			}
+			originTraversal = new StorageTraversal(origin);
+		}
+
+		return new SynchronizationModel(leftTraversal, rightTraversal, originTraversal);
+	}
+
+	/**
 	 * Browses the given traversal in order to create a typed element for the given side of the comparison.
 	 * 
 	 * @param traversal