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Re: third version of semantics document

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 28 Aug 2002 10:48:12 -0400 (EDT)
Message-Id: <20020828.104812.68933172.pfps@research.bell-labs.com>
To: phayes@ai.uwf.edu
Cc: www-webont-wg@w3.org

As an indication of how things can go wrong in a complicated specification,
Pat's document is very close to implying that all RDFS classes and
properties are OWL objects.

Why is this?

First, the extension of the denotations of rdfs:subClassOf and
rdfs:subPropertyOf are transitive relations according to the RDFS model theory.
Second, a resource belongs to the class extension of the denotation of
owl:TransitiveProperty if its extension is transitive. 
Therefore, the denotations of rdfs:subClassOf and rdfs:subPropertyOf belong
to the class extension of the denotation of owl:TransitiveProperty.
Third, owl:TransitiveProperty is an rdfs:subPropertyOf owl:ObjectProperty
and thus of owl:Property.
Therefore, the denotations of rdfs:subClassOf and rdfs:subPropertyOf belong
to the class extension of the denotation of owl:Property.

From this, one might expect that a domain of rdfs:subClassOf and
rdfs:subPropertyOf should be owl:Object.  However, this is written as a
closure rule, not as a semantic condition, so it is not triggered.  If it
was a semantic condition it would imply that all RDF classes and properties
belong to the class extension of the denotation of owl:Object.

peter
Received on Wednesday, 28 August 2002 10:48:24 GMT

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