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Re: SPARQL queries: resource identifier/rdf:about

From: conor dowling <conor@the325project.org>
Date: Mon, 9 May 2005 10:25:00 -0700
Message-Id: <334401e7b370b144c6b4f3442842274d@the325project.org>
Cc: semantic-web@w3.org
To: Jeen Broekstra <jeen@aduna.biz>

first off, thx very much for the info Jeen. One last question on 
"rdf:about" or rather the value of "?subject" ...

>> 2) rdf:about value and value of "?subject"
>> # can I get the "rdf:about" from every resource
>> PREFIX rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
>> SELECT ?subject
>> WHERE { ?subject rdf:about ?about }
> No.
> rdf:about is not an actual property, but is simply a bit of syntax in
> the RDF/XML serialization that is used to denote the subject of a
> triple. It does not occur in the RDF graph and can not be queried
> through SPARQL (or any other RDF query language that I know of).

but is the value returned in ?subject is equivalent to rdf:about in 

SELECT ?subject

Let's say I assign it to a variable "subjectIdentifier". Then can I say 

SELECT ?name
WHERE {subjectIdentifier dc:title ?name}

(assuming of course that dc:title is supported by that subject ...). In 
other words, can I use the subject id's across queries to that data 
source? Is the subject id data source dependent,  nothing more than a 
convenient resource identifier for use within that data source?

>> is this equivalent to (presuming all resources have abouts and aren't 
>> blank)?
>> SELECT ?subject
>> The subject variable is bound to an about uri value OR if blank, a 
>> unique id, scoped to the result. Is that right?
> Not quite. See above.

> # can I get the "rdf:about" from every resource
>> PREFIX rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
>> SELECT ?about
>> WHERE { ?subject rdf:about ?about }
>> WHERE { ?subject rdf:about ?about }
Received on Monday, 9 May 2005 17:25:52 UTC

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