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Re: I can accept... (Was: Re: Objective 4.6: additional semantic knowledge)

From: Pat Hayes <phayes@ihmc.us>
Date: Mon, 17 May 2004 14:54:15 -0500
Message-Id: <p06001f10bccec3db999d@[10.0.100.76]>
To: Kendall Clark <kendall@monkeyfist.com>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>

>On Tue, May 11, 2004 at 04:52:52PM -0700, Rob Shearer wrote:
>
>>  4.6 Additional semantic knowledge
>>  It should be possible for knowledge encoded in other semantic languages,
>>  such as RDFS, OWL, and SWRL to affect the results of queries about RDF
>>  graphs.
>
>In the interests of making progress, I'm willing to accept Rob's
>version, above, of my original proposal.  In the current UC&R doc,
>my original is 4.6 and Rob's variant is 4.6a.
>
>So, I'd be willing to accept a modest reworking of 4.6a:
>
>Additional Semantic Information
>
>It should be possible for knowledged encode din other semantic
>languages -- for example: RDFS, OWL, etc. -- to affect the results of
>queries about RDF graphs.
>
>In fact, unless someone objects, I'd like to make that the language in
>the document and the version which we vote on at some point.

Sorry to rock the boat, but this requirement worries me. It is 
possible to interpret it as saying that a query-responder has a 
licence to use RDFS, OWL, etc., content to respond to any RDF query. 
I think that would be a very bad idea, if the query is unable to 
specify which of the various languages are intended to be used.

Moreover, the term 'semantic language' is not defined, and according 
to some versions of what SWeb meaning boils down to, it could include 
unformatted English inside rdf:comment strings. Already we have a 
potential disagreement over whether SWRL counts as a semantic 
language.

I would be happier if we did not have any such requirement. It seems 
to me to be orthogonal to the query language design, and a matter to 
be handled by an RDFS or OWL inference engine rather than by a 
querying protocol. Our charter explicitly says that the RDF graph 
being queried may be 'virtual' , so it could be an RDFS or OWL 
closure or the virtual graph obtainable from a given graph from a 
particular SWRL rule set: this provides us with a very neat way to 
avoid this issue and keep our attention focused on querying graphs 
rather than drawing inferences which may or may not be valid 
according to a variety of different semantic frameworks.

Finally, the wording suggests that OWL and RDFS are 'other' than RDF, 
whereas in fact they are semantic extensions of RDF.

At the very least, it ought to be possible to do a 'bare RDF' query, 
explicitly rejecting any reliance on any other non-RDF implication or 
machinery, and the requirement, if we keep it, should make this clear.

Suggestion (if we must keep this requirement):

Additional Semantic Information

It should be possible for a query to indicate that the answers should 
take into account knowledge encoded in RDF semantic extensions, such 
as RDFS, OWL, etc..

Pat
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Received on Monday, 17 May 2004 15:54:18 GMT

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