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Re: FAQ: stratified class hierarchies vs. RDFS

From: R.V.Guha <guha@guha.com>
Date: Mon, 24 Jun 2002 14:51:35 -0700
Message-ID: <3D179467.70003@guha.com>
To: pat hayes <phayes@mail.coginst.uwf.edu>
CC: www-rdf-comments@w3.org, Dan Connolly <connolly@w3.org>, Tim Berners-Lee <timbl@w3.org>


 I don't think I was clear enough. The current RDF MT models rdfs:Class 
as denoting a set. I am taking the position that we should consider 
modeling rdf:type is just another relation, i.e., as not having anything 
special in the model theory. It is only when one says that rdfs:Class = 
set of all sets, that one gets into the "set of all sets that don't 
contain themselves" paradox. If you regard rdf:type as just another 
relation (like dc:title or dc:author), we don't have this issue.

I am also further arguing that from a modelling perspective (i.e., 
independent of logical paradox issues) "rdfs:Class = set of all sets" 
does not capture the right intuition about rdfs:Class



pat hayes wrote:

> I don't accept that there are two notions here. rdfs:Class extension 
> are sets; not all sets are rdfs:Class extensions, but that doesn't 
> mean that this is a category distinction of some kind. That position 
> would be very hard to maintain while also giving a model theory.
>> Both approaches are relatively common, with the rdfs:Class approach 
>> being more commonly used in large scruffy implementations and the set 
>> oriented approach being more common in formalizations such as DLs.
>> The important question is, which one do we use to describe concepts 
>> like "Person"? My personal preference is for the cog-sci approach. It 
>> is more pliable and fairly immune to logical nastinesses like paradoxes.
> There is no such approach that is immune from logical nastiness. Come 
> on, Guha, you are the one suggesting that we USE logic to give the 
> semantics for all this. How can you simultaneously be saying that it 
> is cognitive-sciency and therefore un-logical?
Received on Monday, 24 June 2002 17:52:25 UTC

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