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Re: DESCRIBE with GRAPH

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Tue, 22 May 2007 11:28:25 +0100
Message-ID: <4652C5C9.6010402@hp.com>
To: Geoff Chappell <gchappell@intellidimension.com>
CC: public-rdf-dawg-comments@w3.org



Geoff Chappell wrote:
> Hi all,
> 
> I've got a questions about the interaction of DESCRIBE with GRAPH.  
> 
> Given this setup:
> 
> # Default graph (stored at http://example.org/dft.ttl)
> @prefix dc: <http://purl.org/dc/elements/1.1/> .
> <http://example.org/bob>    dc:title  "Bob Hacker" .
> <http://example.org/alice>  dc:title  "Alice Hacker" .
> 
> # Named graph: http://example.org/bob
> @prefix foaf: <http://xmlns.com/foaf/0.1/> .
> <http://example.org/bob> foaf:name "Bob" .
> <http://example.org/bob> foaf:mbox <mailto:bob@oldcorp.example.org> .
> 
> # Named graph: http://example.org/alice
> @prefix foaf: <http://xmlns.com/foaf/0.1/> .
> <http://example.org/alice> foaf:name "Alice" .
> <http://example.org/alice> foaf:mbox <mailto:alice@work.example.org> .
> <http://example.org/bob> foaf:name "Bobby" .
> 
> PREFIX foaf: <http://xmlns.com/foaf/0.1/>
> PREFIX dc: <http://purl.org/dc/elements/1.1/>
> 
> DESCRIBE ?s
> FROM <http://example.org/dft.ttl>
> FROM NAMED <http://example.org/alice>
> FROM NAMED <http://example.org/bob>
> WHERE
> {
>    ?s ?p ?o .
>    GRAPH ?g { ?s foaf:mbox ?mbox }
> }
> 
> 
> Would you expect that the description would draw from any graph that had
> contributed to the result (including the default graph)?

Yes - the description can draw on any graph, or indeed on information not 
available to the query pattern at all (that might not be very useful, of 
course, but maybe adding a timestamp or a signature).

DESCRIBE allows the the server to control the shape of the RDF returned, not 
requiring the client to know details of all data formats and structures 
available. Like any server offering, there will be good offerings and bad 
offerings.

	Andy



> e.g. would the
> description of <http://example.org/bob> be:
> 
> <http://example.org/bob>  dc:title  "Bob Hacker";
> 	foaf:name "Bob";
> 	foaf:mbox <mailto:bob@oldcorp.example.org>.
> 
> or: 
> 
> <http://example.org/bob>  dc:title  "Bob Hacker";
> 	foaf:name "Bob", "Bobby";
> 	foaf:mbox <mailto:bob@oldcorp.example.org>.
> 
> or:
> 
> <http://example.org/bob>  dc:title  "Bob Hacker".
> 
> or...
> 
> I realized that DESCRIBE is somewhat loosely defined, but wondering what
> other implementations have done in this situation. Any guidance
> appreciated....
> 
> Thanks,
> 
> Geoff
> 
> 
> 
> 

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Received on Tuesday, 22 May 2007 10:28:45 GMT

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