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Re: Named Graph Property Path Question

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Mon, 25 Jul 2011 15:48:27 +0100
Message-ID: <4E2D823B.4090908@epimorphics.com>
To: public-rdf-dawg@w3.org
Matt,

Any unbound variable in GRAPH becomes a lop on the URIs known to be in 
the dataset:

eval(D(G), Graph(var,P)) =
      Let R be the empty multiset
      foreach IRI i in D
         R := Union(R, Join( eval(D(D[i]), P) , Ω(?var->i) )
      the result is R

http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#defn_evalGraph

so it tries each one with some value of ?g making the active graph that 
graph "D(D[i])".

eval(D(G), ZeroLengthPath(x:term, path, vy:var)) =
   { { (vy, x) } }
   card[{ (vy, x) }] = 1

so it's (1), repeated or each named graph.

	Andy

On 21/07/11 20:17, Matthew Perry wrote:
> Hi,
>
> I have come across a property path query that I'm not sure about:
>
> SELECT ?g ?o
> WHERE { GRAPH ?g { <urn:s> <urn:p1>{0} ?o } }
>
> Do we get:
> 1) ?o=<urn:s>, ?g=<urn:graph_i> for all graphs in the dataset
> 2) ?o=<urn:s>, ?g=<urn:graph_i> for all graphs in the dataset that
> contain <urn:s> as a subject
> 3) something else
>
> I don't believe we hit the 0-length case with an unbound graph in our
> tests.
>
> Thanks,
> Matt
>
Received on Monday, 25 July 2011 14:49:09 GMT

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