diff --git a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/.ratings b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/.ratings
index e5635e1fa010d51fb11a54185fa471b1bc69a75b..9d0d7f8df1b322b3005d555d7552e4aa62d05156 100644
--- a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/.ratings
+++ b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/.ratings
@@ -1,3 +1,3 @@
-AddMissingAnnotationsMigrationProvider.java 83d2f324d0d1346e4cbcbc9006ad8df3babc6fd2 YELLOW
-RemoveDuplicatedAnnotationsMigrationProvider.java 929e5541de79b6e50e0fad0e21e389265b1528b4 YELLOW
-RemoveOutdatedAnnotationInstanceMigrationProvider.java 9e8a02f1cfcdf5138fdeb53cb968cacd1ba3b703 YELLOW
+AddMissingAnnotationsMigrationProvider.java ebc5b9348b61ffb23493942949ecccf1c1fa2ae1 GREEN
+RemoveDuplicatedAnnotationsMigrationProvider.java 6920909f8f211b9c5b5990644b5abcd8c4abaa3a GREEN
+RemoveOutdatedAnnotationInstanceMigrationProvider.java 245530d6026f9ff29ffc577983d9de03ae5e75e5 GREEN
diff --git a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/AddMissingAnnotationsMigrationProvider.java b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/AddMissingAnnotationsMigrationProvider.java
index 83d2f324d0d1346e4cbcbc9006ad8df3babc6fd2..ebc5b9348b61ffb23493942949ecccf1c1fa2ae1 100644
--- a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/AddMissingAnnotationsMigrationProvider.java
+++ b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/AddMissingAnnotationsMigrationProvider.java
@@ -15,11 +15,11 @@
 +--------------------------------------------------------------------------*/
 package org.fortiss.tooling.base.migration;
 
+import static java.util.Collections.emptyMap;
 import static org.fortiss.tooling.base.utils.AnnotationUtils.instantiateAnnotationsRecursive;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Map;
 
 import org.eclipse.emf.ecore.EObject;
@@ -55,6 +55,6 @@ public class AddMissingAnnotationsMigrationProvider implements IMigrationProvide
 		EObject rootElement = modelElement.getRootModelElement();
 		instantiateAnnotationsRecursive(rootElement);
 		migratedProjects.add(modelElement);
-		return Collections.emptyMap();
+		return emptyMap();
 	}
 }
diff --git a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveDuplicatedAnnotationsMigrationProvider.java b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveDuplicatedAnnotationsMigrationProvider.java
index 929e5541de79b6e50e0fad0e21e389265b1528b4..6920909f8f211b9c5b5990644b5abcd8c4abaa3a 100644
--- a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveDuplicatedAnnotationsMigrationProvider.java
+++ b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveDuplicatedAnnotationsMigrationProvider.java
@@ -15,11 +15,11 @@
 +--------------------------------------------------------------------------*/
 package org.fortiss.tooling.base.migration;
 
+import static java.util.Collections.emptyMap;
 import static org.fortiss.tooling.kernel.utils.EcoreUtils.getChildrenWithType;
 import static org.fortiss.tooling.kernel.utils.EcoreUtils.pickInstanceOf;
 import static org.fortiss.tooling.kernel.utils.LoggingUtils.error;
 
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
@@ -97,6 +97,6 @@ public class RemoveDuplicatedAnnotationsMigrationProvider implements IMigrationP
 		error(ToolingBaseActivator.getDefault(),
 				"Duplicate annotations have been removed from \"" + uri.lastSegment() +
 						"\". Please report this incident since it indicates an internal problem.");
-		return Collections.emptyMap();
+		return emptyMap();
 	}
 }
diff --git a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveOutdatedAnnotationInstanceMigrationProvider.java b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveOutdatedAnnotationInstanceMigrationProvider.java
index 9e8a02f1cfcdf5138fdeb53cb968cacd1ba3b703..245530d6026f9ff29ffc577983d9de03ae5e75e5 100644
--- a/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveOutdatedAnnotationInstanceMigrationProvider.java
+++ b/org.fortiss.tooling.base/src/org/fortiss/tooling/base/migration/RemoveOutdatedAnnotationInstanceMigrationProvider.java
@@ -15,11 +15,11 @@
 +--------------------------------------------------------------------------*/
 package org.fortiss.tooling.base.migration;
 
+import static java.util.Collections.emptyMap;
 import static org.eclipse.emf.ecore.util.EcoreUtil.delete;
 import static org.fortiss.tooling.common.util.LambdaUtils.isAssignableFromAny;
 import static org.fortiss.tooling.kernel.utils.EcoreUtils.getChildrenWithType;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -76,6 +76,6 @@ public abstract class RemoveOutdatedAnnotationInstanceMigrationProvider<T extend
 				delete(annotation);
 			}
 		}
-		return Collections.emptyMap();
+		return emptyMap();
 	}
 }
diff --git a/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/.ratings b/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/.ratings
index aaaabe0a705cc5fcd0e0cd40cc1fe3e9533b594e..b2f23c1f28fd6be6f4cd785dfbd17d06d59c5604 100644
--- a/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/.ratings
+++ b/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/.ratings
@@ -6,7 +6,7 @@ IEclipseResourceStorageLocationProvider.java 0ab7f304d52a9d86f01f66e308e9a7ca420
 IElementCompositor.java 5b0ab1732f71b3f8467e0276c844f0dd549e191f GREEN
 ILibraryElementHandler.java 00ef5b25c63b8570006e6f6748aed0da1f33a5f1 GREEN
 ILogMessageHandler.java 9ab53e836a095ef00fd84ecc0375167edf593b46 GREEN
-IMigrationProvider.java c194c8aaaecc84c6e476231362f7c815592026fc YELLOW
+IMigrationProvider.java 241bfd8594dfb86ce0f89dc95b43662f52d9e450 GREEN
 IPrototypeProvider.java d5e3dbae19b5654caf28b81da6b1609d3c12be12 GREEN
 IStorageProvider.java d9b14cdd254d0c956dc5715c1c4d4d955a705dd5 GREEN
 ITransformationProvider.java a4ee2ea08720bb2fce29806062eb01499bb5071e GREEN
diff --git a/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/IMigrationProvider.java b/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/IMigrationProvider.java
index c194c8aaaecc84c6e476231362f7c815592026fc..241bfd8594dfb86ce0f89dc95b43662f52d9e450 100644
--- a/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/IMigrationProvider.java
+++ b/org.fortiss.tooling.kernel/src/org/fortiss/tooling/kernel/extension/IMigrationProvider.java
@@ -45,11 +45,11 @@ public interface IMigrationProvider extends IObjectAware<ITopLevelElement> {
 	/**
 	 * Applies the provider to the given element.
 	 * 
-	 * The parameter "unknownFeatures" returns a map indicating the features that are not recognized
+	 * The parameter "unknownFeatures" indicates the features that are not recognized
 	 * in the model. This can be useful to detect features coming from old models and can be then
 	 * translated to the new model by a migrator.
 	 * 
-	 * @return all features which were migrated.
+	 * @return all unknown features that have successfully been migrated.
 	 */
 	Map<EObject, AnyType> migrate(ITopLevelElement modelElement,
 			Map<EObject, AnyType> unknownFeatures);