[det]rdf_update(+Subject, 
+Predicate, +Object, ++Action)
[det]rdf_update(+Subject, 
+Predicate, +Object, +Graph, ++Action)Replaces one of the three (four) fields on the matching triples 
depending on Action:
- subject(Resource)
 - Changes the first field of the triple.
 
- predicate(Resource)
 - Changes the second field of the triple.
 
- object(Object)
 - Changes the last field of the triple to the given resource or
literal(Value). 
- graph(Graph)
 - Moves the triple from its current named graph to Graph. This 
only works with rdf_update/5 
and throws an error when used with rdf_update/4.