code: @Override
  	public void checkUniqueNames(Iterable<IEObjectDescription> descriptions, 
  			CancelIndicator cancelIndicator, 
  			ValidationMessageAcceptor acceptor) {
  		Iterator<IEObjectDescription> iter = descriptions.iterator();
  		if (!iter.hasNext())
  			return;
  		Map<EClass, Map<QualifiedName, IEObjectDescription>> clusterToNames = Maps.newHashMap();
  		while(iter.hasNext()) {
  			IEObjectDescription description = iter.next();
  			checkDescriptionForDuplicatedName(description, clusterToNames, acceptor);
  			operationCanceledManager.checkCanceled(cancelIndicator);
  		}
  	}
docs: <p>
  {@inheritDoc}
  </p>
  The cancel indicator will be queried everytime a description has been processed.
  It should provide a fast answer about its canceled state.