- From: Seaborne, Andy <andy.seaborne@hp.com>
- Date: Tue, 22 May 2007 11:14:40 +0100
- To: Olivier Corby <Olivier.Corby@sophia.inria.fr>
- CC: public-rdf-dawg-comments@w3.org
Olivier Corby wrote: > I have a question regarding from named and graph pattern. What happens > when the graph pattern first argument is an URI that does not belong to > the from named list (here, URI3) : > > FROM NAMED URI1 > FROM NAMED URI2 > select * where { > graph ?src { PAT } > graph URI3 { PAT } > } > > > My question is : does the graph URI3 pattern fail ? I think that it is > not easy to answer this question. > > The paragraph below seems to say that it should fail because D[IRI] is > not in D ? Is it what we want ? > > 12.5 Evaluation Semantics > > Definition: Evaluation of a Graph Pattern > > eval(D(G), Graph(IRI,P)) = eval(D(D[IRI]), P) > > > Best regards, > > Olivier Corby > Olivier, This could be more clearly expressed in sec 12 and I've added it to the editorial changes list. The evaluation of eval(D(G), Graph(IRI,P)) for IRI not an IRI of a graph in the dataset should be the empty multiset. The results need to be the same as applying a filter which restricts the graph URI: GRAPH ?g { pattern } FILTER ( ?g = <uri> ) and GRAPH <uri> { pattern } need have the same results, except that the first has ?g bound to <uri>. In the algebra: (filter (= ?g <uri>) (graph ?g ... )) and (graph <uri> ...) or for that matter the hypothetical quad form: (filter (= ?g <uri>) (quadpattern [quad ?g ?s ?p ?o])) and (quadpattern [quad <uri> ?s ?p ?o])) Thanks for pointing this out, Andy -- Hewlett-Packard Limited Registered Office: Cain Road, Bracknell, Berks RG12 1HN Registered No: 690597 England
Received on Tuesday, 22 May 2007 10:14:52 UTC