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Re: Conventions and top-level ontologies for RDF

From: Philippe Martin <Philippe.Martin@sophia.inria.fr>
Date: Tue, 20 Jun 2000 19:25:53 +0200
Message-Id: <200006201725.e5KHPrx11690@strato.inria.fr>
To: www-rdf-interest@w3.org

> ... to state that some classes/properties can't be instantiated:
> AbstractClass (subClassOf: Class)
> B_Class (type: AbstractClass)
> C_Class (subClassOf: B_Class)
> a_object (type: A_Class, type: C_Class)

Then, a_object is instance of a class that should have no instance?
Like Pierre-Antoine CHAMPIN, I am not convinced that "isAlso" permits
more than multi-inheritance.

The notion of class without instance is interesting but does not
distinguish between various notions:
- some things cannot exist according to certain physical laws of
  certain worlds/domains (real or imaginary), or according to 
  certain definitions (e.g. contradictions in terms),
- some things just did not happen in a certain world (e.g. Europe)
  and during a certain time frame,
- some things are imaginary and may or may not have happened in
  some worlds.
Thus, classes such as "AbstractClass" or "NonexistentThing" do not
mean much since they do not specify any world/space/time frame. 
It would be dangerous to add them to a top-level ontology because
some persons would use them directly (without specializing them
adequately first) and it would lead to inconsistencies.
Offering classes for various notions of nonexistence would be 
good. Further work is needed.
There is already the class "ImaginarySpatialEntity" in my 
top-level ontology. It may be somewhat questionable regarding
the world/space/time frame problem but it is a convenient
generalization of classes such as "Unicorn" or "CartoonCharacter".

Any other remark on the proposed conventions and top-level ontology?

> This may not be the usual way to solving this problem. But I like the
> freedom of inventing my own OO. :-)

The less "conventional" the less (automatically) comparable with
metadata that other users have generated, therefore the less reusable.


Dr. Philippe Martin 
Research Fellow at the CRC for Enterprise Distributed Systems Technology 
                       (DSTC Pty Ltd;  DSTC is the Australian W3C Office)
Address: Griffith Uni, School of I.T., PMB 50 GCMC, QLD 9726 Australia
Email: philippe.martin@gu.edu.au
Received on Tuesday, 20 June 2000 13:26:09 UTC

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