fixed bug by implemented the prepareID method for dummy root object.

refs 1098

org.fortiss.tooling.kernel/trunk/src/org/fortiss/tooling/kernel/internal/DummyTopLevelElement.java

@@ -20,8 +20,10 @@ package org.fortiss.tooling.kernel.internal;
 import org.eclipse.core.runtime.Assert;
 import org.eclipse.core.runtime.IProgressMonitor;
 import org.eclipse.emf.common.command.CommandStackListener;
+import org.eclipse.emf.common.util.TreeIterator;
 import org.eclipse.emf.ecore.EObject;
 import org.fortiss.tooling.kernel.extension.data.ITopLevelElement;
+import org.fortiss.tooling.kernel.model.IIdLabeled;
 import org.fortiss.tooling.kernel.service.IPersistencyService;
 
 /**
@@ -120,7 +122,18 @@ final class DummyTopLevelElement implements ITopLevelElement {
 	/** {@inheritDoc} */
 	@Override
 	public void prepareIDs(EObject modelElement) {
-		// ignore
+		if(!(modelElement instanceof IIdLabeled))
+			return;
+
+		int id = Integer.MIN_VALUE;
+		for(TreeIterator<EObject> iter = getRootModelElement().eAllContents(); iter.hasNext();) {
+			EObject o = iter.next();
+			if(o instanceof IIdLabeled) {
+				id = Math.max(id, ((IIdLabeled)o).getId());
+			}
+		}
+
+		((IIdLabeled)modelElement).setId(id + 1);
 	}
 
 	/** {@inheritDoc} */