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RE: possible peculiarity with empty datatypes

From: pat hayes <phayes@ihmc.us>
Date: Tue, 8 Jul 2003 08:57:18 -0500
Message-Id: <p0600125dbb307c5be71d@[10.0.100.7]>
To: <Patrick.Stickler@nokia.com>, "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: <www-rdf-comments@w3.org>

>  > -----Original Message-----
>>  From: ext pat hayes [mailto:phayes@ihmc.us]
>>  Sent: 08 July, 2003 05:40
>>  To: Peter F. Patel-Schneider
>>  Cc: www-rdf-comments@w3.org
>>  Subject: Re: possible peculiarity with empty datatypes
>>
>>
>>
>>  >Hi:
>>  >
>>  >A datatype, d, with an empty value space may end up in an
>>  unusual state
>>  >because it has no instances, and thus would not trigger any
>>  >	x rdf:type d
>>  >semantic conditions (assuming that such semantic conditions
>>  are included in
>>  >RDFS).
>>
>>  My own sense is that there should be no such datatype. I will add
>>  this to the required conditions for a datatype, ie that the value
>>  space is nonempty.
>
>Perhaps better to specify that the lexical space is non-empty,
>which is an equally reasonable constraint, I think, and then
>it will follow from the definition of L2V that the value space
>is thus nonempty.

To be safe Ive added both conditions.  I now realize that the 
datatype entailment rules already assumed this, in fact (otherwise 
rdfD1 might not be valid) and Ive added an Lbase axiom-let to capture 
it: a datatype property is now required to not be universally false.

Pat


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Received on Tuesday, 8 July 2003 09:57:19 GMT

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