On Thu, Oct 31, 2013 at 10:26 AM, Maria Jackson
<[email protected]> wrote:
> Yes I am talking about the same. Is it possible to query over Jena such that
> there is a join between two named graphs. I know I can write using
> reification in SPARQL using:
>
> select ?a?b?c?d?e
> where{
> ?r rdf:subject <Mr_X>.
> ?r rdf:predicate <isPresident>.
> ?r rdf:object <CountryZ>.
> ?r saidBy ?a.
> ?r saidOn ?b.
> ?r saidAt ?c.
> ?r confidence ?d.
> ?r comment ?e
> }
>
> But I am not sure as to how can I write this query using named graphs
> without knowing the names of the graphs. As i am converting from reification
> to named graphs automatically. So the user does not know the names of the
> graphs
If you use the approach I outlined in my first response, so that
you've got something like a graph named:
<http://example.org/comment_by_tia>
with the triple
<MrX> <isPresidentOf> <CountryZ>
and then having some triples around somewhere like
<http://example.org/comment_by_tia> <saidBy> <Tia>
<http://example.org/comment_by_tia> <saidOn> "2013-10-29"^^...
<http://example.org/comment_by_tia> <saidAt> <NewYork>
<http://example.org/comment_by_tia> <confidence> 0.9
<http://example.org/comment_by_tia> <comment> "This is just a
comment by Tia"
you'd retrieve it with
select ?a ?b ?c ?d ?e ?f where {
graph ?r {
<Mr_X> <isPresidentOf> <CountryZ>
}
?r <saidBy> ?a ;
<saidOn> ?b ;
<saidAt> ?c ;
<confidence> ?d ;
<comment> ?e .
}
//JT
--
Joshua Taylor, http://www.cs.rpi.edu/~tayloj/
