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Re: rdfs:Literal question

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 17 Sep 2001 16:57:03 -0500
Message-Id: <p0510100fb7cc2088587f@[205.160.76.175]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
>My take is that it provides a way of characterizing the things that 
>literals denote.
>
>So even if
>   LLL rdf:type rdfs:Literal .
>is not valid syntax, I think it's reasonable to be able to say that LV
>(as in XL: qLiteral -> LV) is the same as ICEXT(I(rdfs:Literal)).

Well, there is something very odd about having a constraint that is 
perfectly clear, perfectly natural, and assumed in the semantics, but 
being unable to say it in the formal language, especially when its 
perfectly clear HOW to say it in the formal language. (Its a bit like 
not being able to assert subclass loops, in fact :-)

>I think this is consistent with the material Aaron refers to in his 
>response to you.  I think that material also hints at the 
>possibility of recognizing different sub-types of rdfs:Literal.

That would be OK, since there the rdfs:Literal would be the value of 
rdfs:subClassOf rather than the subject of something.

Pat

>#g
>--
>
>At 03:23 PM 9/17/01 -0500, Pat Hayes wrote:
>>A question.
>>
>>RDFS has a class named rdfs:Literal. Presumably this is supposed to 
>>be the class of all literal values, right? So it ought to be the 
>>case that for any literal LLL, this would be true:
>>
>>LLL rdf:type rdfs:Literal .
>>
>>But that's syntactically illegal. In fact it is impossible to say 
>>that literal has any properties in RDF, so why do we have a class 
>>in RDFS of things that we aren't allowed to say are in a class?
>>
>>(This came up when I was trying to characterize valid inference in 
>>RDFS, by the way. Sorry if this has been discussed before, but I've 
>>only just noticed it.)
>>
>>Pat Hayes
>>--
>>---------------------------------------------------------------------
>>IHMC                                    (850)434 8903   home
>>40 South Alcaniz St.                    (850)202 4416   office
>>Pensacola,  FL 32501                    (850)202 4440   fax
>>phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
>
>------------------------------------------------------------
>Graham Klyne                    MIMEsweeper Group
>Strategic Research              <http://www.mimesweeper.com>
><Graham.Klyne@MIMEsweeper.com>
>------------------------------------------------------------


-- 
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IHMC					(850)434 8903   home
40 South Alcaniz St.			(850)202 4416   office
Pensacola,  FL 32501			(850)202 4440   fax
phayes@ai.uwf.edu 
http://www.coginst.uwf.edu/~phayes
Received on Monday, 17 September 2001 17:57:00 EDT

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