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Denotation of owl:Class

From: Brian McBride <bwm@hplb.hpl.hp.com>
Date: Fri, 25 Apr 2003 13:35:30 +0100
Message-Id: <5.1.0.14.0.20030425120739.0484ab18@localhost>
To: RDF Core <w3c-rdfcore-wg@w3.org>

I've begun my review of the owl reference document.  An aspect about which 
I have an uncertain feeling of unease concerns the denotation of 
owl:Class.  I would appreciate some guidance from the WG.

Owl introduces a notion of owl:Class, distinct from rdfs:Class with the 
following rationale:

[[
NOTE: owl:Class is defined as a subclass of rdfs:Class. The rationale for 
having a separate OWL class construct lies in the restrictions on OWL DL 
(and thus also on OWL Lite), which imply that not all RDFS classes are 
legal OWL DL classes. In OWL Full these restrictions do not exist and 
therefore owl:Class and rdfs:Class are the same there.
]]

   http://www.w3.org/TR/owl-ref/

What is bothering me is that the denotation of owl:Class seems to depend on 
what is processing it, and I guess I'm making the naive user assumption, 
that owl:Class denotes the same thing (horribly deep philosophical rathole 
opens in front of me) wherever its used i.e. either

   rdfs:Class rdfs:subClassOf owl:Class .

is true in the 'real world' or its not.  If its true, then why is owl:Class 
needed?  If its false, why is OWL FULL asserting its true.

So I guess the naive user assumption is wrong, or maybe I'm interpreting it 
naively.  Perhaps owl:Class denotes the "principle class type of the 
processor that is processing this document".  That seems pretty scary too.

I guess I should assume that I'm out of my depth here.  Can someone please 
explain in short simple words what owl:Class denotes and why its needed.

Brian
Received on Friday, 25 April 2003 08:34:49 EDT

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