Fixed comment

refs 1943

org.fortiss.tooling.kernel/trunk/src/org/fortiss/tooling/kernel/internal/storage/eclipse/ModelContext.java

@@ -58,7 +58,7 @@ import org.fortiss.tooling.kernel.utils.UniqueIDUtils;
  * @author hummel
  * @author $Author$
  * @version $Rev$
- * @ConQAT.Rating YELLOW Hash: A7B00E66E3893E14F4097D435147ACFC
+ * @ConQAT.Rating YELLOW Hash: 1E09DC71D8E0EBDD16B88FD1C86085D6
  */
 class ModelContext implements ITopLevelElement, CommandStackListener {
 
@@ -87,10 +87,13 @@ class ModelContext implements ITopLevelElement, CommandStackListener {
 	private int maxId = -1;
 
 	/**
-	 * TODO (dan): I do not understand this comment
-	 * The map containing the unknown features. Can be non-empty, in which case the migrators have
-	 * to deal with it.
-	 * Only if they don't the model context is buggy.
+	 * There might be mismatches between the meta-model of a file and the meta-model of AF3
+	 * (typically when using a file saved with an older version of AF3). In this case, the parser
+	 * will parse the file (or fail if the file is really too different from what is expected), but
+	 * it will also return the XML nodes ("features") that it failed to parse. These are stored in a
+	 * map "EObject to AnyType": EObject gives the context in which the unknown feature has been met
+	 * and AnyType provides the actual unknown data. If non-empty, the migrators have to deal with
+	 * it. If they don't the model context is considered buggy.
 	 */
 	private Map<EObject, AnyType> unknownFeatures;