W3C home > Mailing lists > Public > public-owl-dev@w3.org > January to March 2011

Re: Despair! The exact meaning of Complement??

From: Alan Rector <rector@cs.man.ac.uk>
Date: Mon, 28 Feb 2011 09:26:08 +0000
Cc: Owl Dev <public-owl-dev@w3.org>, Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>, Pat Hayes <phayes@ihmc.us>
Message-Id: <EC237373-97DA-4AD4-AD03-50C76E7E925B@cs.man.ac.uk>
To: dja222@hotmail.com

On 28 Feb 2011, at 00:30, Pat Hayes wrote:

>>> And another: Is it allowed to make the most upper class "Thing" equivalent to a defined class?
> No. Even if it is strictly legal, it would be a very bad idea, as an ontology that did this would be immediately inconsistent with almost every other ontology. 

Inferring that some class is equivalent to owl:Thing is a not uncommon error.  The simple form is that any class with the definition: 

	C EquivalentClass (A or not A)

is equivalent to owl:Thing. 

Hopefully no one would do this intentionally, but it can come about as the result of other inferences.  Matthew Horridge has some difficult-to-spot examples from his work on justifications.    The result is usually a mass of unintended inferences, since everything is inferred to be a subclass of C. 

In general, a useful heuristic is that, if you find an unexpected inference of equivalence in your ontology, you have probably made a mistake. 


Alan Rector
Professor of Medical Informatics
School of Computer Science
University of Manchester
Manchester M13 9PL, UK
TEL +44 (0) 161 275 6149/6188
FAX +44 (0) 161 275 6204
Received on Monday, 28 February 2011 09:26:38 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 20:58:20 UTC