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 ---------------------- 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 www.cs.man.ac.uk/~rector www.co-ode.org http://clahrc-gm.nihr.ac.uk/
Received on Monday, 28 February 2011 09:26:38 UTC