W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > November 2001

RE: Literals: lexical spaces and value spaces

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Wed, 14 Nov 2001 09:45:05 -0600
Message-Id: <p0510104fb818412c0d22@[65.212.118.147]>
To: Graham Klyne <Graham.Klyne@MIMEsweeper.com>
Cc: w3c-rdfcore-wg@w3.org
>At 07:38 PM 11/13/01 -0600, you wrote:
>>I was under the impression that XML Schema datatypes DID satisfy 
>>the required conditions. To fail, we need the following 
>>circumstances: two datatypes D1 and D2 with the value space of D1 
>>being a subset of that of D2, and the lexical space of D1 
>>intersecting that of D2, and D1 having a different, and 
>>incompatible, lexical-to-value mapping on that intersection from 
>>that used by D2.
>
>I'm still bothered by the way you're describing this.  The problem I 
>understand you're trying to avoid is that RDF(S) inferences may end 
>up licensing incompatible literal datatype mappings.

Right.

>  I would expect the above to read:
>
>[[[
>... To fail, we need the following circumstances: two datatypes D1 and D2
>     with any instance of D1 being inferable to also be an instance of D2,
>     ********************************************************************
>and the lexical space of D1 intersecting that of D2, and D1 having a 
>different, and incompatible, lexical-to-value mapping on that 
>intersection from that used by D2.
>]]]
>
>In RDF(S), I understand that value space subsetting is not, of 
>itself, sufficient to draw subclass inferences.  Am I wrong?  (I 
>understand DAML+OIL is different.)

No, you are right, and I was being sloppy. I should have said 
something like: ....the value space of D1 being an rdfs:subClassOf 
that of D2...., referring of course to the extensions.

But you know, I feel that a datatyping scheme that would break - not 
just barf, but give wrong answers - when subclass reasoning was 
extensionally accurate, was far too 'fragile' for practical use, even 
if it could be made to work on paper.

Pat
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Received on Wednesday, 14 November 2001 10:44:43 EST

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