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Re: SPARQL, named graphs and default graph

From: Nuutti Kotivuori <naked@iki.fi>
Date: Wed, 13 Sep 2006 18:08:52 +0300
To: Chimezie Ogbuji <ogbujic@bio.ri.ccf.org>
Cc: Richard Cyganiak <richard@cyganiak.de>, public-sparql-dev@w3.org
Message-ID: <874pvbajnf.fsf@aka.i.naked.iki.fi>

Chimezie Ogbuji wrote:
> I don't agree.  What's the source of this assertion? I think the
> core issue here is that there is *no* concensus formalism for named
> graphs WRT RDF, yet SPARQL is dependent on an RDF model that
> supports named graphs.  If there is one, please point me to it,
> because I ran across the same problem when constructing programming
> APIs for named graphs.  The only formalism I know of is Graham Kyle,
> John McCarthy's work [1].

Well, one thing which would help me in this is a survey of the
approaches other people have taken when doing these things.

I think I know the situation with Redland librdf, when I read the code
last, but I'm not sure if I'm correct.

I think that in librdf, there are statements explicitly without a
context. In SPARQL queries, the default graph is the merge of all
statements in the store, with or without a context. Queries which
explicitly match the graph in a variable never match statements
without a context. And so there is no easy way to match all the
statements without a context only.

I'd like to know atleast how rdflib and Jena (with whatever extensions
that this requires) solve this issue.

-- Naked
Received on Wednesday, 13 September 2006 15:09:00 GMT

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