OWL/DAML+OIL "Tricks of the Trade / How To Do It":
Closed World Reasoning Example

Author:  Deborah L. McGuinness



Title - Closed World Reasoning.

Task/Modeling problem - Include a notion of closed world reasoning in an OWL or DAML+OIL knowledge base. There are many examples of closed world reasoning but this example includes two common cases.
State that the known values for a particular property on a particular individual are the only values for that property on that individual. Assume for example, that there is an individual instance of the class "Person" named "Deborah" with a property "hasCar" with a value "Saab900Turbo". The task is to allow a reasoner to infer that Deborah only has the saab (and no new distinct individuals will be added as values to her hasCar property).

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