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
On Thu, Oct 31, 2013 at 7:50 PM, Joshua TAYLOR <[email protected]>wrote:
> On Thu, Oct 31, 2013 at 9:47 AM, Maria Jackson
> <[email protected]> wrote:
> > I think jena employs named graphs as a way to achieve reification. As
> named
> > graphs can achieve reification by attaching only one statement with named
> > graphs.
>
> Jena uses named graphs to provide names for RDF graphs as specified in
> the SPARQL standards. It's not about reification, it's about having
> more than one graph. It's not unlike the fact that Wikipedia has a
> bunch of articles that can be identified by their URLs; it's not
> about refification, it's about providing different articles and not
> having just one big article.
>
> > Is it possible to express information of the following form using named
> > graphs, if yes then can someone please help me write this information
> using
> > named graphs, so that I may import the same into Jena:
> >
> > _:a rdf:subject "Mr X".
> > _:a rdf:predicate "isPresident".
> > _:a rdf:object "countryZ".
> > _:a saidBy "Tia".
> > _:a saidOn "29 October 2013".
> > _:a saidAt "New York".
> > _:a confidence 0.9.
> > _:a comment "This is just a comment by Tia".
> >
> > Is it possible to write the corresponding query Jena using named graph
> > query on the above given data?
>
> You'll need to clarify what you're trying to do here. You can already
> store this data in a named (or in an unnamed) RDF graph. Maybe what
> you're talking about doing is having a graph named (e.g.)
>
> <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"
>
> This would be convenient way to provide a sort of reification,
> especially because you could put more than one triple in the named
> graph, so the "meta-information" could be describing a collection of
> triples. Is this the sort of thing that you're talking about doing?
>
> //JT
> --
> Joshua Taylor, http://www.cs.rpi.edu/~tayloj/
>
