W3C home > Mailing lists > Public > www-webont-wg@w3.org > August 2002

How to do it/Tricks of the trade for closed world reasoning

From: Deborah McGuinness <dlm@KSL.Stanford.EDU>
Date: Wed, 28 Aug 2002 18:52:16 -0700
Message-ID: <3D6D7E50.A7E902EF@ksl.stanford.edu>
To: webont <www-webont-wg@w3.org>

ACTION: Deb to take a shot at writing up the closed world example

I wrote up a simple example of closed world reasoning in:

http://www.ksl.stanford.edu/people/dlm/daml/closedWorld.html

This just counts the number of values on a property on an individual and
asserts that maximum cardinality restriction on that property for the
individual.
This is the simplest notion of closed world reasoning that we can
capture.
I have done some other work (with borgida and hull) on attempting to
close off an entire individual
and put the work down a few years ago when it was more complicated than
we anticipated.
I will also add a summary of where we left off in a more complicated
example.

i am enclosing the contents of the url above for archiving purposes for
the list.
I used a combination of Guus's how to do it style and my previous tricks
of the trade style.

d

==========
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.



--
 Deborah L. McGuinness
 Knowledge Systems Laboratory
 Gates Computer Science Building, 2A Room 241
 Stanford University, Stanford, CA 94305-9020
 email: dlm@ksl.stanford.edu
 URL: http://ksl.stanford.edu/people/dlm/index.html
 (voice) 650 723 9770    (stanford fax) 650 725 5850   (computer fax)
801 705 0941
Received on Wednesday, 28 August 2002 21:50:31 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:57:51 GMT