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Re: Owl abstract syntax, equivalent classes

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 09 May 2003 14:55:29 -0400 (EDT)
Message-Id: <20030509.145529.123561358.pfps@research.bell-labs.com>
To: gk@ninebynine.org
Cc: public-webont-comments@w3.org

From: Graham Klyne <gk@ninebynine.org>
Subject: Owl abstract syntax, equivalent classes
Date: Tue, 06 May 2003 17:07:03 +0100

> With reference to:
>    http://www.w3.org/TR/owl-semantics/syntax.html#2.3.2.1
> 
> I see:
> [[
> axiom ::= 'DisjointClasses(' description description { description } ')'
>          | 'EquivalentClasses(' description { description } ')'
>          | 'SubClassOf(' description description ')'
> ]]
> 
> which appears to admit "EquivalentClasses( description )" as a valid axiom.
> 
> Is this correct?  If so, what does it mean?  I'm guessing there's a missing 
> "description" in the EquivalentClasses production.  (Assuming this is so, I 
> see no cause to raise a formal comment.)

This is correct.  Allowing EquivalentClasses( description ) means that
blank node descriptions with no connections to other descriptions are
allowed, as per a request from Jeremy Carroll.  Such unconnected
blank node descriptions have no semantic import.

Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies
Received on Friday, 9 May 2003 14:55:40 GMT

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