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Re: a possible syntax error in equivalentProperty/premises005 ?

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Sat, 15 Nov 2003 10:49:18 +0000
Message-ID: <16310.1198.588621.564423@merlin.horrocks.net>
To: <minsu@etri.re.kr>
Cc: <public-webont-comments@w3.org>

On November 15, Minsu Jang writes:
> 
> Hi,
> 
> While I'm testing and browsing W3C OWL test cases, I found a strange
> premise document.
> The premise doc is
> http://www.w3.org/2002/03owlt/equivalentProperty/premises005,
> and a fragment from the doc follows.
> 
> 	<owl:Restriction rdf:nodeID="d">
> 		<owl:onProperty rdf:resource="#p"/>
> 		<owl:onProperty rdf:resource="#q"/>
> 		<owl:hasValue rdf:resource="#v"/>
> 	</owl:Restriction>
> 
> According to AS&S, this looks invalid, because restrictions can have
> only one
> individualvaluedPropertyID or datavaluedPropertyID.

This is not invalid (it would be nice if it were, but one of the
"benefits" of the RDF syntax is that it is very hard to constrain
syntactic forms to those that are intended). I would strongly
recommended, however, that you do not use this form as the semantics
are probably not what is intended - it is equivalent to a restriction
using either one of the properties, plus an axiom asserting that the
two restrictions (one for each property) are equivalent classes. I.e.,
something like (modulo syntax errors):

	<owl:Restriction rdf:nodeID="d">
		<owl:onProperty rdf:resource="#p"/>
		<owl:hasValue rdf:resource="#v"/>
	</owl:Restriction>

	<owl:Restriction rdf:nodeID="d">
		<owl:onProperty rdf:resource="#p"/>
		<owl:hasValue rdf:resource="#v"/>
	        <owl:equivalentClass>
			<owl:Restriction rdf:nodeID="d">
			<owl:onProperty rdf:resource="#q"/>
			<owl:hasValue rdf:resource="#v"/>
			</owl:Restriction>
	        </owl:equivalentClass>
	</owl:Restriction>

If we had a semantic search engine I would be able to point you to a
number of emails in the WG archive that discuss this issue, but
I can't find them with the current search engine :-(

Regards, Ian



> 
> But, Jena[1] and OWL Ontology Validator[2] successfully parse the
> document.
> I'm confused. Any comments on this?
> 
> Minsu
> 
> [1] Jena: http://jena.sourceforge.net/
> [2] OWL Ontology Validator:
> http://phoebus.cs.man.ac.uk:9999/OWL/Validator
> 
> --------------------------------------------------
> Minsu Jang
> Senior Member of Engineering Staff
> Business Knowledge Research Team
> Electronics and Telecommunications Research Institute
> Phone: +82-42-860-1250 Fax: +82-42-860-6790 
> 
Received on Saturday, 15 November 2003 05:53:50 GMT

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