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Re: Final text for Basic Graph Patterns

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 19 Jan 2006 11:33:33 -0600
Message-Id: <p06230901bff574dc3ff8@[]>
To: Enrico Franconi <franconi@inf.unibz.it>
Cc: Dan Connolly <connolly@w3.org>, Bijan Parsia <bparsia@isr.umd.edu>, RDF Data Access Working Group <public-rdf-dawg@w3.org>

>On 18 Jan 2006, at 23:12, Pat Hayes wrote:
>>>>SELECT ?x WHERE {:a rdf:type ?x .}
>>>Look, this is not a legal OWL-DL query.
>>This query pattern has legal OWL-DL instances, so why is it not a 
>>legal OWL-DL query?
>Look, we already agreed that we are not here to do research.

Of course. You miss my point. I was simply following the general 
pattern of how SPARQL queries are defined, using our most recent 
attempt at an 'entailment-based' general form of definition, and 
applying that to OWL-DL as described in the OWL spec, and seeing what 
we finish up with. ( {:a rdf:type :b} is legal OWL-DL, under 
appropriate constraints, and is an instance of the query under 
binding of a variable to a legal OWL-DL identifier, so... ) I meant 
only that if one takes a 'natural' extension of SPARQL to OWL, 
keeping the basic form of the definitions but replacing simple 
entailment by OWL-DL entailment, then examples like this turn up. I 
do not mean to quarrel with what you have done or suggest it should 
have been done in any other way.

The only reason for our discussing this matter at all *in this forum* 
is because some folk - notably, Bijan and yourself - have argued 
forcibly that the SPARQL definitions should be couched in a way which 
generalizes naturally to the OWL case, by replacing 'simply entails' 
with 'OWL-DL entails' in the definitions. That is what I did.

>First of all, I have been sloppy in my statement, since OWL-DL 
>queries do not exist - we are defining them now here. Now, there is 
>*no* theoretical nor practical result that even considers queries of 
>that kind in the DL literature.

I do not dispute this. As I said, I was simply applying the proposed 
SPARQL definitions to OWL-DL (as defined in the OWL specs). If this 
gets us to an area that has not yet been explored in the research 
literature, that seems to me to be in fact an extremely good reason 
for NOT including ANY mention of OWL in the SPARQL documents at all, 
other than perhaps an informative warning that this is an open 
problem area unsuitable for standardization at the present.


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Received on Thursday, 19 January 2006 17:33:46 UTC

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