- From: Stephen Reed <reed@cyc.com>
- Date: Thu, 15 Aug 2002 13:28:44 -0500 (CDT)
- To: Dan Brickley <danbri@w3.org>
- cc: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, <guha@guha.com>, <www-rdf-logic@w3.org>
On Thu, 15 Aug 2002, Dan Brickley wrote: [with regard to quantification over predicates (properties) in CycL] > Interesting. Thanks for the example/pointers. Having implemented this, can > you folks comment on whether such language features have proved > problematic, useful etc...? Input from folk who've implemented large scale > KR systems is one of the reasons we set up www-rdf-logic. In Cyc, rules constitute only 5% of the KB content, ground facts are the remainder. And among the rules only a small fraction quantify over predicates. So I would summarize our experience with higher order logic as useful for a few cases, yet worth including if your goal is symbolically representing the full range of world phenomena. And because we have special case inference engine support for the common higher order query cases, we avoid much generic rule backchaining for them. Because Cyc has over 10,000 predicates (relationships between objects) it is a challenge for the user to correctly specify the appropriate predicate to express a desired relationship. Although we now have RKF (Rapid Knowledge Formation) tools to assist this search and clarification, the primary use of quantification over predicates has been in queries. You can ask for example which predicates hold between concepts by making the predicate position a variable in the query. I can imagine a query language for OWL that allows variables in the property position, even though quantification over properties is not part of the asserted OWL language. -Steve -- =========================================================== Stephen L. Reed phone: 512.342.4036 Cycorp, Suite 100 fax: 512.342.4040 3721 Executive Center Drive email: reed@cyc.com Austin, TX 78731 web: http://www.cyc.com download OpenCyc at http://www.opencyc.org ===========================================================
Received on Thursday, 15 August 2002 14:28:56 UTC