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Re: Punning and the "properties for classes" use case (from public-owl-dev)

From: Alan Ruttenberg <alanruttenberg@gmail.com>
Date: Tue, 6 Nov 2007 12:39:34 -0500
Message-Id: <B7F13F30-80C6-4BB9-87F6-CC8A2EE1FB04@gmail.com>
Cc: ian.horrocks@comlab.ox.ac.uk, jjc@hpl.hp.com, schneid@fzi.de, public-owl-wg@w3.org
To: Peter F. Patel-Schneider <pfps@research.bell-labs.com>

On Nov 6, 2007, at 5:14 AM, Peter F. Patel-Schneider wrote:

>> But why couldn't we, with punning, for instance, have Class(C) entail
>> Individual(C) to more closely match the OWL Full case? Then we too
>> would have a domain size of 1 be inconsistent (because of the
>> presence of the individuals owl:Thing and owl:Nothing)?
> But nothing says that these two individuals are different.

They have different size extensions. Isn't that enough? If they were  
the same they would have to have the same extensions.

>> Wouldn't the entailments match in that case? - both would be
>> inconsistent, and hence both would entail anything.
> Nope.  You can't even get away in general by using unique names
> assumption to pump up the size of the domain.  OWL Full has only
> infinite domains (because its domains contain lots of bits of syntax),
> and this has observable consequences.  For example, a spy point  
> ontology
> that restricts the domain to maximum size 1 000 000 is satisfiable in
> OWL DL but not in OWL Full.

Is there an easy way to show this (for my collection of OWL examples?)

>> In order to do this, we would need to, effectively, assert an
>> individual of the same name as  each entity(class or property) in the
>> ontology. While I can imagine why this might be considered
>> distasteful, would it work from a technical point of view as far as
>> getting us closer to OWL Full alignment?
> No.

OK. Follows from the fact that Full domains are infinite.

What about going the other way? Jeremy mentioned that David Turner  
proposed some axioms that, if I understood things correctly, would  
assert owl:Thing to be infinite even in the DL case. (he'll send a  
followup email with the details). This may not be desirable from the  
point of view of wanting DL to be able to be finite to enable certain  
types of computation, like some approximations of closed-world- 
reasoning, but I want to separate that out and understand the  
technical issues, if you will help me.

Received on Tuesday, 6 November 2007 17:39:51 UTC

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