* executing the LDPath program
*/
private void copyLdPath(UriRef uri, RDFBackend<Object> rdfBackend,
Set<String> langs, MGraph graph, Lock writeLock) throws DereferenceException {
//A RdfReference needs to be used as context
RdfReference context = valueFactory.createReference(uri);
//create the representation that stores results in an intermediate
//graph (we do not want partial results on an error
MGraph ldPathResults = new SimpleMGraph();
RdfRepresentation result = valueFactory.createRdfRepresentation(uri, ldPathResults);
//execute the LDPath Program and write results to the RDF Graph