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Re: Comments on SPARQL (reification)

From: Dan Connolly <connolly@w3.org>
Date: Mon, 16 May 2005 12:25:53 -0500
To: Ashok Malhotra <ashok.malhotra@oracle.com>
Cc: eric@w3.org, andy.seaborne@hp.com, public-rdf-dawg@w3.org, w3c-xsl-query@w3.org
Message-Id: <1116264353.11315.90.camel@localhost>

On Mon, 2005-05-16 at 09:17 -0700, Ashok Malhotra wrote:
> Notes on SPARQL Query Language for RDF
> W3C Working Draft 17 February 2005

i.e. http://www.w3.org/TR/2005/WD-rdf-sparql-query-20050217/

note that there's a newer one...

> How is reification supported?  That is, how does SPARQL handle values that are themselves triples?

Just like it handles all other values.

SELECT ?st ?s ?p ?o WHERE { ?st rdf:subject ?s; rdf:predicate ?p;
rdf:object ?o }.

Note that SPARQL variables bind to terms, not their values;
so ?st will get bound to a bNode (or URI) that denotes
a statement.

>   I assume nested queries are required

No; nothing special is required. Reification is just
a utility vocabulary; it's treated like dublin core
or FOAF as far as SPARQL is concerned.

> but there is no discussion of support for this important aspect of RDF.

Hmm... perhaps we should have an example in the spec or a
test case. This question seems to come up now and again.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
see you at XTech in Amsterdam 24-27 May?
Received on Monday, 16 May 2005 19:48:02 UTC

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