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Re: comments on http://www.w3.org/TR/2002/WD-rdf-schema-20021112/

From: pat hayes <phayes@ai.uwf.edu>
Date: Sat, 30 Nov 2002 21:57:38 -0600
Message-Id: <p05111b07ba0cea1884d3@[10.0.100.247]>
To: "Richard H. McCullough" <rhm@cdepot.net>
Cc: w3c-rdfcore-wg@w3.org
>Yes, I am assuming that two classes with the same members are the same class.

RDFS doesn't make that assumption (although it is *consistent* with 
that, if you want to assume it.) Think of 'class' as meaning 
something like 'classification category' or 'concept', eg it is 
traditional to distinguish the concepts 'hairless bipedal arthropod' 
and 'human' even though they have the same instances. RDFS allows 
such 'intensional' usages.

>
>If that is not true of rdfs:Class, then either
>1. you are talking about "currently known members" of a class
>or
>2. you are talking about two "different contexts",
>i.e., two different ways of viewing the same individuals,
>with two different sets of relations to other classes.
>
>If 1. or 2. is not true, then you're not talking about reality.

We are simply allowing intensional distinctions between concepts 
which happen to 'accidentally' have the same instances. That is 
perfectly coherent, and indeed has been argued to be a desireable 
property of a description language by many eminent authorities.

Pat Hayes

>============
>Dick McCullough
><http://rhm.cdepot.net/>knowledge := man do identify od existent done
>knowledge haspart list of proposition
>
>----- Original Message -----
>From: <mailto:bwm@hplb.hpl.hp.com>Brian McBride
>To: <mailto:rhm@cdepot.net>Richard H. McCullough ; 
><mailto:www-rdf-comments@w3.org>www-rdf-comments@w3.org
>Sent: Wednesday, November 27, 2002 5:39 AM
>Subject: Re: comments on 
><http://www.w3.org/TR/2002/WD-rdf-schema-20021112/>http://www.w3.org/TR/2002/WD-rdf-schema-20021112/
>
>At 05:03 27/11/2002 -0800, Richard H. McCullough wrote:
>
>[...]
>>##### I agree.  I just got lazy.  I didn't have a printout of the
>>document, and I was trying to manage by flipping between screens.  BTW,
>>the document has no section numbers or page numbers.
>
>Right.  Will fix.
>
>[...]
>>##### OK, here's the proof that your definition of Class is contradictory.
>>##### I don't remember exactly what you said in the rdf interest discussion.
>>##### I think the basic idea was that "Class" is a class instead of a set
>>of class names.
>>##### The problem with your definition comes out when you consider
>>##### the PROPER subclass relations between Class and Resource.
>>##### By the definition of Resource
>>#####        every class except Resource is a proper subclass of Resource
>
>I think this falls at the first hurdle.  I hearby define eg:Class, a class
>that is not a proper subclass of rdfs:Resource.
>
>    eg:Class      rdf:type        rdfs:Class .
>    eg:Class      rdfs:subClassOf rdfs:Resource .
>    rdfs:Resource rdfs:subClassOf eg:Class .
>
>Are you assuming that two classes with exactly the same members must be the
>same class?  This is not true of rdfs:Class.
>
>Brian


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Received on Saturday, 30 November 2002 23:54:28 EST

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