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Predicate rdf_update/4
Availability::- use_module(library(semweb/rdf_db)).
Source[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.
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Wouter Beek said (2017-10-28T13:02:00):0 upvotes 0 0 downvotes
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Notice that use of this predicate may result in duplicates:

?- [library(semweb/rdf_db)].
?- rdf_assert(a, b, c, x).
?- rdf_assert(a, b, c, y).
?- rdf_update(a, b, c, graph(z)).
?- rdf(S, P, O, G), writeln(rdf(S,P,O,G)), fail.
rdf(a,b,c,z).
rdf(a,b,c,z).
false.

In library(semweb/rdf11) this is fixed by disallowing the use of graph/1 for argument Action.