/** @see org.eclipse.gef.commands.Command#undo() */
 public void undo() {
   oldSource.removeOutput(newIncomingTransition);
   oldTarget.removeInput(newOutgoingTransition);
   newActivity.removeInput(newIncomingTransition);
   newActivity.removeOutput(newOutgoingTransition);
   parent.removeChild(newActivity);
   oldSource.addOutput(transition);
   oldTarget.addInput(transition);
 }
 /** @see org.eclipse.gef.commands.Command#execute() */
 public void execute() {
   oldSource.removeOutput(transition);
   oldTarget.removeInput(transition);
   parent.addChild(newActivity);
   newIncomingTransition = new Transition(oldSource, newActivity);
   newOutgoingTransition = new Transition(newActivity, oldTarget);
 }