Re: Comments on SPARQL (reification)

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...
http://www.w3.org/TR/2005/WD-rdf-sparql-query-20050419/

> 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/
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