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Re: RDF Review

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Fri, 3 Oct 2003 12:09:41 +0100
Message-ID: <16253.22773.568243.714802@galahad.cs.man.ac.uk>
To: pat hayes <phayes@ihmc.us>
Cc: www-webont-wg@w3.org, Jeff Pan <panz@cs.man.ac.uk>

This looks fine to me.

Ian

On October 2, pat hayes writes:
> 
> >Dear All,
> >
> >Jeff and I (mostly Jeff) have looked at the latest RDF MT, in
> >particular the Datatypes section. We did not have time for an
> >exhaustive review, but here are some comments:
> >
> >Regards, Ian
> >========================================
> 
> Further to my last message, here is a proposed text for the relevant 
> part of section 7. This effectively defines 'datatype clash' more 
> broadly to cover all the various cases, including the ill-formed 
> literal cases.
> 
> ----------------------
> 
> If the datatypes in the datatype map D impose disjointness conditions 
> on their value spaces, it is possible for an RDF graph to have no 
> D-interpretation which satisfies it. For example, XML Schema defines 
> the value spaces of xsd:string and xsd:decimal to be disjoint, so it 
> is impossible to construct a XSD-interpretation satisfying the graph
> 
> <ex:a> <ex:b> "25"^^xsd:decimal .
> <ex:b> rdfs:range xsd:string .
> 
> This situation could be characterized by saying that the graph is 
> XSD-inconsistent, or more generally as a datatype clash. Note that it 
> is possible to construct a satisfying rdfs-interpretation for this 
> graph, but it would violate the XSD conditions, since the class 
> extensions of I(xsd:decimal) and I(xsd:string) would have a nonempty 
> intersection.
> 
> Datatype clashes can arise in several other ways. For example, any 
> assertion that something is in both of two disjoint dataype classes:
> 
> _:x rdf:type xsd:string .
> _:x rdf:type xsd:decimal .
> 
> or that a property with an 'impossible' range has a value:
> 
> <ex:p> rdfs:range xsd:string .
> <ex:p> rdfs:range xsd:decimal .
> _:x <ex:p> _:y .
> 
> would constitute a datatype clash. A datatype clash may also arise 
> from the use of a particular lexical form, for example:
> 
> <ex:a> <ex:p> "2.5"^^xsd:decimal .
> <ex:p> rdfs:range xsd:integer .
> 
> or by the use of an ill-typed lexical form:
> 
> <ex:a> <ex:p> "abc"^^xsd:integer .
> <ex:p> rdfs:range xsd:integer .
> 
> Datatype clashes are the only inconsistencies recognized by this 
> model theory ; note however that datatype clashes involving XML 
> literals can arise in RDF and RDFS.
> 
> -----------
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Received on Friday, 3 October 2003 07:11:18 GMT

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