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RE: problems with RDF datatyping

From: <Patrick.Stickler@nokia.com>
Date: Fri, 17 Jan 2003 16:21:46 +0200
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B160C9D@trebe006.europe.nokia.com>
To: <bwm@hplb.hpl.hp.com>, <w3c-rdfcore-wg@w3.org>, <phayes@ai.uwf.edu>



> -----Original Message-----
> From: ext Brian McBride [mailto:bwm@hplb.hpl.hp.com]
> Sent: 17 January, 2003 13:32
> To: rdf Core; pat hayes
> Subject: Fwd: problems with RDF datatyping
> 
> 
> 
>  From PFPS:
> 
> >In trying to make the OWL semantics correspond to the RDF 
> semantics I came
> >up with the following problems in RDF datatyping:
> >
> >1/ A datatype is an element of IR, because the RDF MT says 
> that datatypes are
> >denoted by URI references.  However, rdf:XMLLiteral is said to be a
> >datatype, but rdf:XMLLiteral is a URI reference.  Something 
> is wrong here.

rdf:XMLLiteral denotes the datatype. It is not itself the datatype.
It is a URIref.

> >2/ XSD-interpretations include in their datatypes the XML 
> Schema datatypes
> >that are problematic when removed from XML documents or have other
> >problems.  XSD-interpretations also include, for example, 
> the datatype
> >named FOO, which is not defined as an XML datatype.

I'm not really sure what your saying here.

I'm not aware of any XML Schema datatype that does not conform
to the definition of rdfs:Datatype.

Can you be more specific?

> >3/ A datatype has to be more than is specified in the RDF 
> MT.  Except for
> >XSD-interpretations, which explicitly mention the 
> URI-reference to datatype
> >relationship, there is no way of tying the intended 
> URI-reference for a
> >datatype to that datatype.  For example, if I have D 
> containing a datatype
> >for integers and a datatype for strings, there is no way to 
> require that a
> >particular URI reference, say ex:int, denotes the integer datatype.
> >
> >
> >It probably makes more sense to say that a datatype is a four-tuple,
> >consisting of a URI reference, a lexical space, a value space, and a
> >lexical-to-value mapping.

This doesn't make sense to me. A URIref is a name. It denotes 
something. A name is not part of the thing it denotes. It is
fully concievable that there can be multiple URIrefs that denote
the same datatype, just as there can be e.g. multiple URIrefs
that denote the city of Paris, France. A URIref denoting the
city of Paris is not part of the city of Paris.

Further, one can use OWL mechanisms to express such equality
of denotation if in fact multiple URIrefs denote the same
datatype.

I would consider the inclusion of the URIref as part of the
datatype definition a mistake.

Regards,

Patrick
Received on Friday, 17 January 2003 09:21:54 EST

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