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Re: Asserting subclasses of open ranges or domains

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Wed, 9 Sep 2009 18:00:01 +0200
Message-ID: <9d93ef960909090900v7a3f1ec9k10a496336c98e1dd@mail.gmail.com>
To: Pat Hayes <phayes@ihmc.us>
Cc: "Paulheim, Heiko" <heiko.paulheim@sap.com>, "ontolog-forum@ontolog.cim3.net" <ontolog-forum@ontolog.cim3.net>, "semantic-web@w3.org" <semantic-web@w3.org>
Thanks Pat to jump in this

> We could as well define a tautological class dcterms:Topic as the range of
> dcterms:Subject, and assert only subclasses.
> Is that clearer?
> What is not clear is why you want to do this. Even in the case of the
> domestic appliances, if you do not put any necessary conditions on this
> class, you have effectively said nothing.

OK. I'm certainly dumb, but in what is this different, say, from the
definition of the class foaf:Agent at http://xmlns.com/foaf/spec/#term_Agent
This class has no superclass, hence no necessary condition. Right?
It has two declared subclasses foaf:Person and foaf:Organisation. Those
provide sufficient conditions, hence nothing if I understand well.
foaf:Agent the domain and range of some properties, but this again provides
also sufficient conditions. Right?

Would you say that foaf:Agent is not defined and even useless, since it has
no necessary condition?

The same for many top classes in many ontologies. No?

Thanks for clarifying this.

> It is tricky to appeal to intuition in cases like this, because of course
> we all know that there are things that are not domestic appliances, and we
> tend to use this knowledge without being told that we have to. But our
> ontologies only know stuff like this if we somehow tell them it explicitly.

Indeed. Nobody argues on that :))


Bernard Vatant
Senior Consultant
Vocabulary & Data Engineering
Tel:       +33 (0) 971 488 459
Mail:     bernard.vatant@mondeca.com
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Received on Wednesday, 9 September 2009 16:00:43 UTC

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