KIF Axioms of Restriction

I have a question regarding the notion of Restriction. In order to
understand this notion, I looked at "Annotated DAML+OIL Ontology Markup" and
at the KIF axioms.
According to Axiom 88, the restriction class ?r is defined as all those ?i's
for which the implication (PropertyValue ?p ?j) => (Type ?j ?c) is true.
This means that that if
(PropertyValue ?p ?i ?j) holds, (Type ?j ?c) must hold, too. This is clear.
I thought that the intent was that ?i should be in ?r whenever both
(PropertyValue ?p ?i ?j) and (Type ?j ?c) are true. But the implication is
true also when (PropertyValue ?p ?i ?j) is false. Consequently, class ?r
contains lots of objects, not necessarily related to the property ?p. It
seems that in most cases it would be even infinite. To be sure that my
interpretation of this KIF axiom was correct I asked Richard Fikes. Here is
his statement:

"I think you are correct.  Namely, a class of type Restriction with a
toClass restriction C and an onProperty restriction P is the class of
all objects all of whose values of property P are type C.  That includes
all objects that have no value for property P."

He also suggested that this question should be posted to this list for
discussion. The question is whether this is the intent of the language
designers?


==Mitch Kokar
  Verstatile Information Systems, Inc.

Received on Friday, 9 March 2001 10:55:42 UTC