Re: [Bigdata-developers] RDR for context

[Bryan T. <br...@sy...>]

We do not (yet) support RDF*/SPARQL* (aka RDR) for quads.  However, it is
easy enough to model quads.

<<:bob foaf:age 25>> inGraph <:graph1>

This would give you something that had a concept of a named graph container
(:graph1) but used only the indices for a triple store (SPO, POS, OSP)
rather than the 6 indices for a quad store.  Since the namespace would be
in a triples mode, it would not understand the GRAPH ?g syntax in SPARQL.
(The equivalent semantics could be obtained by writing an RDR triple
pattern to pull out the inGraph statements, but you need to watch out for
how you handle the same statement appearing in more than one graph.  The
"default graph" semantics say that the only the distinct triples are
visited by the triple pattern.  This is in contrast to named graph queries
in which the distinct quads are visited.  More or less.  The actual
definition has to do with the RDF merge of the triples in the named graphs
that are visible to the query and is all pretty complex.)

However, if you have a bunch of statements that naturally can be clustered
into "graphs" and you want the metadata to be about the graph and not the
individual statements in that graph, then just use quads.

We do have RDR support for quads on the roadmap.

Thanks,
Bryan


----
Bryan Thompson
Chief Scientist & Founder
SYSTAP, LLC
4501 Tower Road
Greensboro, NC 27410
br...@sy...
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On Wed, Apr 15, 2015 at 4:55 PM, Max Ott <ma...@ni...> wrote:

> Hi,
>
> While the RDR extension would seem to fit my use case very well, it seems
> to be limited to a single statement. What I would need is being able to
> describe contexts (as in the fourth element of a quad store). Something
> along the lines of:
>
> @prefix : <http://bigdata.com> .
> @prefix foaf: <http://xmlns.com/foaf/0.1/> .
> @prefix dct:  <http://purl.org/dc/elements/1.1/> .
>
> <<:bob foaf:age 25; foaf:name "Bobby".>> dct:creator <
> http://example.com/crawlers#c1> ;
>                      dct:source <http://example.net/bobby.html> .
>
> Unfortunately, that doesn't seem to be supported. Or am I missing
> something?
>
> Do I just need to forget about RDR in this case and figure out on how to
> do this with named graphs and quads? It's really the query side which I'm
> focusing now.
>
> Any help would be greatly appreciated.
> -max
>
>
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