RE: Cutting the Patrician datatype knot

Date: 11/28/01

> -----Original Message-----
> From: ext Peter F. Patel-Schneider 
> []
> Sent: 24 November, 2001 09:16
> To: Stickler Patrick (NRC/Tampere)
> Cc:;
> Subject: RE: Cutting the Patrician datatype knot
> From:
> Subject: RE: Cutting the Patrician datatype knot
> Date: Fri, 23 Nov 2001 20:57:49 +0200
> [...]
> > 
> > If the data type does not define a lexical space, then
> > no mechanism is going to work. Either there's a defined
> > mapping from lexical form to value or there isn't. It
> > is therefore enough to identify that pairing of lexical
> > form (literal) to data type (URI) in order to denote the
> > value.
> The problem is not that the datatypes don't meet your 
> conditions above, the
> problem occurs when two datatypes share some data values, but 
> disagree on
> how to to the lexical-to-value mapping.  If the typing comes 
> from RDF(S),
> then it may be the case that a literal gets these two 
> datatypes.  Then the
> value for that literal is ambiguous.

The value*S* are not ambigous. In the case where there are
multiple pairs of lexical forms and data types, each pair
denotes a value in the value space of the data type. If those
values are not the "same" then we have a contradiction.

Contradictions are part of general life in the semantic web,

By basing the data typing solution on the *pairing* of lexical
form to data type, where the data type defines both lexical
and value space, then we are free to employ whatever idioms
we choose to define such pairings and interpretation is reliable,
even when we have contradictory assertions. E.g.

   x eg:property [ rdf:value "10"; rdf:type xsd:gDay ] .
   eg:property rdfs:range xsd:gMonth .

resulting in the contradiction that "10" is a lexical form
denoting a day value *and* a month value. In both cases,
the pairing is crystal clear


Whether the values denoted by those pairings are the same, and
whether there is a contradiction is a matter for the application.

RDF has done its part by making the pairings clear and available
for such interpretation.




Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email:


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