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Re: Rich semantics and expressiveness

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Thu, 22 Feb 2007 20:14:52 +0100
Message-ID: <45DDEBAC.3090204@mondeca.com>
To: pratt@cs.stanford.edu
Cc: semantic-web@w3.org

Hi Vaugham

> On the other hand if you make expressiveness a semantic notion then 
> you run into the problem of the semantics for "complementOf(D)".  For 
> D = "registered Democrats," are Santa's elves and the states of bliss 
> in complementOf(D)? How do OWL-DL users typically use complementOf, 
> and what do they think it means?
See http://www.w3.org/TR/2004/REC-owl-guide-20040210/#ComplexClasses
In section 5.1.3
"Therefore, a typical usage pattern for /complementOf/ is in combination 
with other set operators"
Which means (as the NonFrenchWine class shows) the typical usage is 
relative complement, as in your examples below. Relative complements are 
intersections, so you can't define relative complement if you have not 
the notion of absolute complement. :-)
> Relative complement is not so problematic, e.g. dogs that aren't 
> Dalmatians, or voters that aren't registered Democrats.  It's also ok 
> to have dogs that aren't registered Democrats or voters that aren't 
> Dalmatians provided the ontology admits the intersection of dogs and 
> voters as a class (a competent type-checking ontology might object to 
> this class on the ground that dogs don't vote, as a way of catching 
> more errors).  Absolute complement  however seems neither terribly 
> useful nor terribly tractable from either a theory or implementation 
> standpoint, and so doesn't seem like a strong selling point for OWL-DL 
> over OWL-Lite.

-- 

*Bernard Vatant
*Knowledge Engineering
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Received on Thursday, 22 February 2007 19:15:02 UTC

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