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RE: TexasThings and owl:equivalentThing

From: Smith, Michael K <michael.smith@eds.com>
Date: Thu, 18 Dec 2003 11:33:39 -0600
Message-ID: <2928D6FE55D5584390909578CAC8397D06061D3D@usplm216.txpln.us.eds.com>
To: Ian Horrocks <horrocks@cs.man.ac.uk>, Bernard Vatant <bernard.vatant@mondeca.com>
Cc: public-webont-comments@w3.org

Bernard,

I meant to respond last week but was swamped.  Of course you are correct.
This will be corrected in next version.

- Mike

Michael K. Smith (+1-512-404-6683)



-----Original Message-----
From: Ian Horrocks [mailto:horrocks@cs.man.ac.uk] 
Sent: Thursday, December 18, 2003 4:19 AM
To: Bernard Vatant
Cc: public-webont-comments@w3.org
Subject: Re: TexasThings and owl:equivalentThing



Bernard,

Good points. Hopefully this can be fixed by the Guide editors.

Ian

On December 15, Bernard Vatant writes:
> 
> 
> Seems to me that there is something wrong, or at least misleading with the
> example of "TexasThings"
> http://www.w3.org/TR/owl-guide/#equivalentClass1
> 
> <owl:Class rdf:ID="TexasThings">
>   <owl:equivalentClass>
>     <owl:Restriction>
>       <owl:onProperty rdf:resource="#locatedIn" />
>       <owl:allValuesFrom rdf:resource="#TexasRegion" />
>     </owl:Restriction>
>   </owl:equivalentClass>
> </owl:Class>
> 
> First it would certainly be better to have the singular "TexasThing"
rather
> than plural "TexasThings" :)
> 
> "TexasThings are exactly those things located in the Texas region ..."
> 
> This is obviously wrong. There is an allValuesFrom, but not a
> someValuesFrom here. As defined, it means : If TexasThings are located
> somewhere, they are located in Texas region.
> 
> An further on
> 
> " ... The difference between using owl:equivalentClass here and using
> rdfs:subClassOf is the difference between a necessary condition and a
> necessary and sufficient condition. With subClassOf, things that are
> located in Texas are not necessarily TexasThings. But, using
> owl:equivalentClass, if something is located in Texas, then it must be in
> the class of TexasThings."
> 
> ... but not the other way round, unfortunately.
> 
> In fact under this definition any thing located nowhere is a Texas Thing.
> Thinking about it, maybe it makes sense after all. Nowhere is indeed in
> Texas, and especially its middle ... :))
> 
> Bernard Vatant
> Senior Consultant
> Knowledge Engineering
> Mondeca - www.mondeca.com
> bernard.vatant@mondeca.com
> 
Received on Thursday, 18 December 2003 12:34:16 GMT

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