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Re: Final text for Basic Graph Patterns

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Thu, 19 Jan 2006 10:39:20 -0500
Message-Id: <e306397a764d9a666c445bc9649ddfaa@isr.umd.edu>
Cc: Dan Connolly <connolly@w3.org>, RDF Data Access Working Group <public-rdf-dawg@w3.org>, Pat Hayes <phayes@ihmc.us>, Enrico Franconi <franconi@inf.unibz.it>
To: Bijan Parsia <bparsia@isr.umd.edu>

On Jan 19, 2006, at 9:10 AM, Bijan Parsia wrote:
[snip]
> (To see this compare:
> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> PREFIX ns:  <http://www.mindswap.org/ontologies/oedipus#>
>
> SELECT ?x
> FROM <http://www.mindswap.org/ontologies/oedipus>
> WHERE { ?x ns:hasChild ?y .
>         ?y rdf:type ns:Patricide .
>         ?y ns:hasChild ?z .
>         ?z rdf:type ns:NotPatricide }
>
> and the same query where ?Y is in the select clause. Frankly, what I 
> *like* about this error is that it's easy to explore 
> (non)distinguishedness without having to go through the GP replacing 
> variables right and left. Oh well.)

Thinking about this a bit more, is there any reason *other* than 
performance, given bnodes in bindings, to have distinguished variables? 
I.e., why not have this query give the same number of answers 
regardless of whether you are using ?y or _:y? And allow projection of 
the bnode.

I don't know what's the more desirable default. (You could use a filter 
isURI or something like K to recover distinguished variables).

Cheers,
Bijan.
Received on Thursday, 19 January 2006 15:39:26 GMT

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