Observation - DAML+OIL and OWL do not make the closed world reasoning assumption, i.e., they do not assume that information that is not known to be true is false. They work with an "open world reasoning" assumption, i.e., they assume that information that is currently not known may become known in the future. Thus, just because Deborah only has one known value for a hasCar property does not mean that she may not have more cars. Said another way, there is no implicit maximum cardinality restriction on Deborah's hasCar property.
Abstracted solution -
Count the number of values for a property
on an individual and then
assert a max cardinality on that
property for that individual.
Example solution -
In this particular case, we would add a maximum cardinality
restriction of 1 on Deborah's hasCar property.
This would allow reasoners to infer that no additional
distinct values for Deborah's hasCar property may be
added (without first removing the value of Saab900Turbo).
Notes -
This solution is the same as the notion of closing
a role in the CLASSIC description logic.
More issues on closing roles can be found in:
- Ronald J. Brachman , Deborah L. McGuinness , Peter F. Patel-Schneider
, Lori Alperin Resnick , and Alex Borgida. ``Living with CLASSIC: When
and How to Use a KL-ONE-Like Language,'' in John Sowa, ed., Principles
of Semantic Networks: Explorations in the representation of knowledge ,
Morgan-Kaufmann: San Mateo, California, 1991, pages 401--456. http://www.ksl.stanford.edu/people/dlm/papers/living-with-classic-abstract.html
-Alex Borgida, Rick Hull, Deborah McGuinness.
On the Confluence of the Closing Order
in Description Logic Knowledge Bases.
Working Draft.
Last Update: August 27, 2002