Index: src/main/java/org/apache/jackrabbit/core/nodetype/NodeTypeDefDiff.java
===================================================================
--- src/main/java/org/apache/jackrabbit/core/nodetype/NodeTypeDefDiff.java	(Revision 514641)
+++ src/main/java/org/apache/jackrabbit/core/nodetype/NodeTypeDefDiff.java	(Arbeitskopie)
@@ -339,8 +339,39 @@
 
         return maxType;
     }
+    
+    public String toString() {
+        String result = this.getClass().getSimpleName() + "[\n\tnodeTypeName="
+                + oldDef.getName();
 
-    //--------------------------------------------------------< inner classes >
+        result += ",\n\tpropertyDifferences=[\n";
+        result += toString(propDefDiffs);
+        result += "\t]";
+
+        result += ",\n\tchildNodeDifferences=[\n";
+        result += toString(childNodeDefDiffs);
+        result += "\t]\n";
+        result += "]\n";
+
+        return result;
+    }
+
+    private String toString(List childItemDefDiffs) {
+        String result = "";
+        for (Iterator iter = childItemDefDiffs.iterator(); iter.hasNext();) {
+            ChildItemDefDiff propDefDiff = (ChildItemDefDiff) iter.next();
+            result += "\t\t" + propDefDiff;
+            if (iter.hasNext()) {
+                result += ",";
+            }
+            result += "\n";
+        }
+        return result;
+    }
+
+
+
+	//--------------------------------------------------------< inner classes >
     abstract class ChildItemDefDiff {
         protected final ItemDef oldDef;
         protected final ItemDef newDef;
@@ -414,6 +445,42 @@
             return oldDef != null && newDef != null
                     && !oldDef.equals(newDef);
         }
+
+		public String toString() {
+            String typeString = "unknown";
+            switch (getType()) {
+                case NONE:
+                    typeString = "NONE";
+                    break;
+                case TRIVIAL:
+                    typeString = "TRIVIAL";
+                    break;
+                case MINOR:
+                    typeString = "MINOR";
+                    break;
+                case MAJOR:
+                    typeString = "MAJOR";
+                    break;
+            }
+
+            String operationString;
+            if (isAdded()) {
+                operationString = "ADDED";
+            } else if (isModified()) {
+                operationString = "MODIFIED";
+            } else if (isRemoved()) {
+                operationString = "REMOVED";
+            } else {
+                operationString = "NONE";
+            }
+
+            ItemDef itemDefinition = (oldDef != null) ? oldDef : newDef;
+
+            return getClass().getSimpleName() + "[itemName="
+                    + itemDefinition.getName() + ", type=" + typeString
+                    + ", operation=" + operationString + "]";
+        }
+
     }
 
     public class PropDefDiff extends ChildItemDefDiff {
Index: src/main/java/org/apache/jackrabbit/core/nodetype/NodeTypeRegistry.java
===================================================================
--- src/main/java/org/apache/jackrabbit/core/nodetype/NodeTypeRegistry.java	(Revision 514641)
+++ src/main/java/org/apache/jackrabbit/core/nodetype/NodeTypeRegistry.java	(Arbeitskopie)
@@ -362,24 +362,32 @@
             notifyReRegistered(name);
             return entNew;
         }
+        
+       	String message = "The following nodetype change contains non-trivial changes."
+                + "Up until now only trivial changes are supported."
+                + " (see javadoc for "
+                + NodeTypeDefDiff.class.getName()
+                + "):\n" + diff.toString();
+        throw new RepositoryException(message);
 
-        // make sure existing content would not conflict
-        // with new node type definition
-        checkForConflictingContent(ntd);
-
-        // unregister old node type definition
-        internalUnregister(name);
-        // register new definition
-        EffectiveNodeType entNew = internalRegister(ntd);
-
-        // persist modified node type definitions
-        customNTDefs.remove(name);
-        customNTDefs.add(ntd);
-        persistCustomNodeTypeDefs(customNTDefs);
-
-        // notify listeners
-        notifyReRegistered(name);
-        return entNew;
+// TODO Implement checkForConflictingContent()
+//        // make sure existing content would not conflict
+//        // with new node type definition
+//        checkForConflictingContent(ntd);
+//
+//        // unregister old node type definition
+//        internalUnregister(name);
+//        // register new definition
+//        EffectiveNodeType entNew = internalRegister(ntd);
+//
+//        // persist modified node type definitions
+//        customNTDefs.remove(name);
+//        customNTDefs.add(ntd);
+//        persistCustomNodeTypeDefs(customNTDefs);
+//
+//        // notify listeners
+//        notifyReRegistered(name);
+//        return entNew;
     }
 
     /**