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Re: some initial comments on SPARQL Query Language for RDF revision 1.596 of 19 December 2005

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Wed, 21 Dec 2005 16:14:59 +0000
Message-ID: <43A97F83.7040805@hp.com>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
CC: public-rdf-dawg-comments@w3.org

Peter,



> [Jumping the gun a little bit.]

No problem; comments welcome on the editors' working draft.

> 
> I just read over the first few sections of SPARQL Query Language for RDF
> revision 1.596 of 19 December 2005, and I have a few concerns:
> 
> 0/ I am disappointed that this is all that can be obtained from DAWG.
> Nevertheless this document is much better than the previous one.
> 
> 1/ This appears to be quite a change.  Will there be some description of what
> the change amounts to?
> 
> 2/ The definitions put much more of a burden on the RDF graph-generating
> process.  I think that this needs to be addressed much more fully.  In
> particular, I think that it would be useful to explain that some systems store
> a particular RDF graph that is not related to an input RDF graph by any
> relationship sanctioned by the RDF recommendations.  Directly querying such RDF
> graphs could result in pecular answers. As well, I think that it would be
> useful to indicate that if querying results approximating RDF entailment or
> RDFS entailment are desired, then the RDF graph that is being queried will be,
> of ncecessity, not explicitly stored anywhere.

I don't understand the points here.  Could you provide an example of the 
burden and the peculiar answers that might be obtained?  Is this related to 
your previous comment on lean graphs?

The document does not cover how a system might store a graph (if it stores it 
at all - it  might be partially calculated on demand) although we have to 
recognize any implementation matters that arise.

	Andy

> 
> 3/ I think that it would be useful to indicate that the only purpose of the wording
> "whose range is a subset of the set of RDF terms occuring in G" is to prevent
> having an infinite number of answers.  I don't think that it eliminates
> "redundancy" in answers, as I believe that the query 
> 	?a r ?b .
> against the graph 
> 	_:a r _:b .
> will have two answers.
> 
> 4/ I don't see why Section 2.9 is included.  I believe that it changes
> nothing.  I believe that it only serves to provide the illusion that there is
> something special about RDF reification.
> 
> 5/ I don't understand why Section 3.1.4 is included.  Yes, producing an RDF
> graph that is the D-entailment closure of another RDF graph can lead to
> additional matches, but this is the case for any augmentation process.  Why
> then signal out D-entailment in this way?  It only serves to provide the
> illusion that there is something special going on.
> 
> 6/ I believe that Section 3.4 is not correct and needs to be removed from the
> document.  
> 
> Probably more later,
> 
> peter
> 
> 
> 
Received on Wednesday, 21 December 2005 16:15:25 GMT

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