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response to semantics comment pfps-01

From: pat hayes <phayes@ai.uwf.edu>
Date: Mon, 3 Feb 2003 16:50:49 -0600
Message-Id: <p05111b25ba64a0a1d19a@[10.0.100.86]>
To: w3c-rdfcore-wg@w3.org
Some XML Schema primitive datatypes are impossible to use as RDF
datatypes.  Therefore XSD intepretations are ill-defined.

The problematic datatypes include:
duration - because equality in its value space is not well defined
QName - because there is no fixed lexical-to-value mapping
ENTITY - because there is no fixed value space
NOTATION - because there is no fixed lexical space
----

I don't consider these to be fatal problems which make it 
'impossible' to use these datatypes. What is true however is that 
these are examples of *underdetermined* datatypes, ie datatypes about 
which the available information is incomplete in some way.

For example, the set of durations is underdetermined; what this means 
is that *any* set which conforms to the XSD spec will suffice as a 
value space of xsd:duration, and there may be more than one such set. 
There may therefore be more XSD interpretations than the XML authors 
intended. As usual in such situations, the effect on inference is 
that some inferences simply cannot be made, eg it is simply unknown 
whether or not one xsd:duration literal can be substituted for 
another, so to this extent the corresponding inference rule does not 
apply. The text makes it clear that these rules apply only in cases 
where certain kinds of information are provided by the datatype 
information source.

In sum, I don't think there is any need to do anything about this 
issue, except possibly to add some explanatory prose to clarify the 
point.

Pat

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Received on Monday, 3 February 2003 17:49:08 EST

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