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Re: Circular definition of Thing?

From: David Allsopp <d.allsopp@signal.qinetiq.com>
Date: Mon, 10 Mar 2003 13:37:27 +0000
Message-ID: <3E6C9517.3C358315@signal.qinetiq.com>
To: "Roger L. Costello" <costello@mitre.org>
CC: www-rdf-logic@w3.org

"Roger L. Costello" wrote:
> Hi Folks,
> Here's how the OWL Reference defines the class Thing:
> <Class rdf:ID="Thing">
>     <rdfs:label>Thing</rdfs:label>
>     <unionOf rdf:parseType="Collection">
>         <Class rdf:about="#Nothing"/>
>         <Class>
>               <complementOf rdf:resource="#Nothing"/>
>         </Class>
>     </unionOf>
> </Class>
> <Class rdf:ID="Nothing">
>     <rdfs:label>Nothing</rdfs:label>
>     <complementOf rdf:resource="#Thing"/>
> </Class>
> Isn't this a "circular definition", i.e., not very informative?  /Roger


The useful information is that

a) Thing is not Nothing (and vice versa) 

b) All instances belong to the class Thing (and therefore no instances
belong in Nothing)

Looking closely at the definition of Thing, the class used in the
unionOf could be any class - Nothing is used for convenience, so things
(ahem) are not as circular as they seem; the definitions do actually
capture the nature of the classes.

E.g. Everything (all instances) is either Apple or NOT Apple - this
would do just as well.


David Allsopp

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Received on Monday, 10 March 2003 08:36:31 GMT

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