W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > January 2003

Re: Fwd: problems with RDF datatyping

From: pat hayes <phayes@ai.uwf.edu>
Date: Sun, 19 Jan 2003 23:12:00 -0800
Message-Id: <p05111b05ba514ac47ae0@[10.0.100.248]>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: pfps@research.bell-labs.com, w3c-rdfcore-wg@w3.org

>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.

Nothing is wrong here. "rdf:XMLLiteral" is a uriref, and it denotes 
rdf:XMLLiteral, a resource which is a datatype. Peter seems to be 
making a use/mention confusion. But in any case, IR *can* contain 
urirefs, eg one can quote a uriref as a string.

>>
>>2/ XSD-interpretations include in their datatypes the XML Schema datatypes
>>that are problematic when removed from XML documents or have other
>>problems.

They might, but that is not our problem or our business. We are 
required by charter to integrate RDF with the XSD datatypes.

>>  XSD-interpretations also include, for example, the datatype
>>named FOO, which is not defined as an XML datatype.

I fail to follow this point. It seems to be false, insofar as I can 
understand it.

>>
>>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.

We do not specify it, but that is not the same as saying that it 
cannot be done. Seems to me that it can be done simply by fiat: I can 
publish a document which simply asserts that the uriref 
http://www.coginst.uwf.edu/~phayes/myexample#octalinteger denotes the 
datatype consisting of the integers with octal lexical forms. Viola.

I anticipate that agreed methods of formally specifying the 
denotations of Urirefs will emerge. But that is not our business.

>>  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.

Who is to say whether or not there is no way to require a URIref to 
denote a datatype? The RDF MT does not specify how this is to be 
done, but there is no reason why it should. But it is not impossible 
for someone to specify this in any way they feel like doing. I do not 
think that this is, or should be, an issue we need to be concerned 
with: it is part of a much larger issue of attaching meanings to 
urirefs.

>>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.

We could do that, but since we say that they are triples and are 
denoted by urirefs, the two formulations seem to me to be essentially 
equivalent.

Pat

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Received on Monday, 20 January 2003 12:51:16 EST

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