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Re: SOURCE issue - querying and retrieval of source

From: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
Date: Tue, 24 Aug 2004 17:16:26 +0100
To: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-ID: <20040824161626.GJ22252@login.ecs.soton.ac.uk>

On Tue, Aug 24, 2004 at 03:02:13 +0100, Dave Beckett wrote:
> 2) Source URI in results
> 
> A query may return a Source URI, separate from binding a Source URI
> in a matching triple or constraint.
> 
> BRQL Example:
> The graph contains aggregated RSS feeds and the query wants to
> return all items indicating where they were originally retrieved
> from, even with duplicates:
> 
>   SELECT ?s WHERE
>     SOURCE ?s (?x rdf:type rss:item)
> 
> The following could be forbidden, while still allowing the above:
>   SELECT ?x,?y,?z WHERE
>     SOURCE <http://www.w3.org/2000/08/w3c-synd/home.rss> (?x ?y ?z)

I think this can be dealt with cleanly by having source = NULL (or a
single bNode) for all triples in stores with no SOURCE support.

So, SOURCE <http://www.w3.org/2000/08/w3c-synd/home.rss> (?x ?y ?z) would
be false, SELECT ?s WHERE SOURCE ?s (?x rdf:type rss:item) would return
NULL for all triples. Should be easy to implement.

- Steve 
Received on Tuesday, 24 August 2004 16:16:33 GMT

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