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[OK] Re: [OK?] Re: comments on "SPARQL Query Language for RDF" (Non-respect for RDF Semantics)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 03 Mar 2006 08:02:20 -0500 (EST)
Message-Id: <20060303.080220.100611064.pfps@research.bell-labs.com>
To: eric@w3.org
Cc: connolly@w3.org, public-rdf-dawg-comments@w3.org

I believe that the current design admits modes in which my concern is correctly
handled.  I would prefer a design that required what I view as the correct
behaviour, but I will not object to the current design.

For the record, the issue shows up when querying an RDF store that has been
given  
     ex:a ex:p ex:c .
     ex:a ex:p _:c .
The behaviour of SPARQL depends on the behaviour of the RDF store.  The RDF
store might end up leaning its input, and thus only store
     ex:a ex:p ex:c .
or it might maintain the input "as is".  My view is that both stores are
"correct", and that querying should not be able to distinguish between the two
behaviours. 

However, the SPARQL basic query 
 	ex:a ex:p ?c .
would (most likely) have one match in the leaning case, but two matches in
the non-leaning case.  (This also depends on just how the scoping graph is
determined.) 

Peter F. Patel-Schneider
Bell Labs Research


From: "Eric Prud'hommeaux" <eric@w3.org>
Subject: [OK?] Re: comments on "SPARQL Query Language for RDF" (Non-respect for RDF Semantics)
Date: Fri, 3 Mar 2006 07:37:51 -0500

> The current definitions relate SPARQL queries to RDF MT entailment.
> Does that address your issue?
> 
> On Thu, Sep 08, 2005 at 08:08:11AM -0500, Dan Connolly wrote:
> > 
> > On Thu, 2005-09-08 at 06:37 -0400, Peter F. Patel-Schneider wrote:
> > > From: Dan Connolly <connolly@w3.org>
> > > Subject: Re: comments on "SPARQL Query Language for RDF" (Non-respect for RDF Semantics)
> > > Date: Wed, 07 Sep 2005 22:26:54 -0500
> > [...]
> > > > The technical point you make is clear. If you can elaborate on what
> > > > makes this a show-stopper, i.e. what one would want to do with SPARQL
> > > > that one cannot do with the design as is, that would be even
> > > > more helpful.
> > > 
> > > My view is that this turns interoperating RDF implementations into
> > > non-interoperating implementations.  For example, an RDF implementation that
> > > leans (RDF Semantics, Section 0.3) any graph it stores can interoperate with
> > > one that doesn't, at least in my reading of the RDF Core WG documents.
> > 
> > I see. Thanks.
> > 
> > 
> 
> -- 
> -eric
Received on Friday, 3 March 2006 13:02:30 GMT

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