[namedgraphs] SPARQL over named graphs with blank nodes

[Blom, J.J.C. (Jaap) <jb...@cr...>]

Hi,

I'm working on NG4J 0.9.3 and have the following code:
                Node graph1 = Node.createURI("http://graph1");
                Node graph2 = Node.createURI("http://graph2");
                Node start = Node.createURI("http://start");
                Node predicate1 = Node.createURI("http://predicate1");
                Node predicate2 = Node.createURI("http://predicate2");
                Node result1 = Node.createLiteral("expected result");
                Node result2 = Node.createLiteral("not expected result");
                NamedGraphSet ngs = new NamedGraphSetImpl();
                ngs.addQuad(new Quad(graph1, start, predicate1, Node.createAnon(new AnonId("blank"))));
                ngs.addQuad(new Quad(graph1, Node.createAnon(new AnonId("blank")), predicate2, result1));
                ngs.addQuad(new Quad(graph2, Node.createAnon(new AnonId("blank")), predicate2, result2));//*/
                String query =
                        "Select ?target Where\n" +
                        "{\n" +
                        "       <" + start.getURI() + "> <" + predicate1.getURI() + "> ?b .\n" +
                        "       ?b <" + predicate2.getURI() + "> ?target\n" +
                        "}";
                System.out.println(query);
                Query sparqlQuery = QueryFactory.create(query);
                QueryExecution qe = QueryExecutionFactory.create(sparqlQuery, new NamedGraphDataset(ngs));
                ResultSet results = qe.execSelect();
                while(results.hasNext())
                {
                        System.out.println(results.next());
                }
                System.out.println("done");

This gives the following result:
Select $target Where
{
        <http://start> <http://predicate1> ?b .
        ?b <http://predicate2> $target
}
( ?target = "expected result" )
( ?target = "not expected result" )
done

I didn't expect the "not expected result", since it is linked to a blank node in another graph. Granted the blank nodes have the same label, but RDF states that blank nodes in different graphs are not linked by their label. Am I correct in this one and if so is this a NG4J error or a Jena/ARQ error?

Greetings,
  Jaap Blom



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