Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!cbatt!ucbvax!SAIL.STANFORD.EDU!VAL From: VAL@SAIL.STANFORD.EDU.UUCP Newsgroups: mod.ai Subject: Seminar - Circumscriptive Query Answering (SU) Message-ID: <8701290647.AA03893@ucbvax.Berkeley.EDU> Date: Mon, 26-Jan-87 17:34:00 EST Article-I.D.: ucbvax.8701290647.AA03893 Posted: Mon Jan 26 17:34:00 1987 Date-Received: Fri, 30-Jan-87 01:51:15 EST Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 35 Approved: ailist@sri-stripe.arpa Commonsense and Nonmonotonic Reasoning Seminar A QUERY ANSWERING ALGORITHM FOR CIRCUMSCRIPTIVE AND CLOSED-WORLD THEORIES Teodor C. Przymusinski University of Texas at El Paso Thursday, January 29, 4pm Bldg. 160, Room 161K McCarthy's theory of circumscription appears to be the most powerful among various non-monotonic logics designed to handle incomplete and negative information in knowledge representation systems. In this presentation we will describe a query answering algorithm for circumscriptive theories. The algorithm is based on a modified version of ordered linear resolution (OL-resolution), which we call a MInimal model Linear Ordered resolution (MILO-resolution). MILO-resolution constitutes a sound and complete procedure to determine the existence of minimal models satisfying a given formula. Our algorithm is the first query evaluation algorithm for general circumscriptive theories. The Closed-World Assumption (CWA) and its generalizations, the Generalized Closed-World Assumption (GCWA) and the Extended Closed-World Assumption (ECWA), can be considered as special forms of circumscription. Consequently, our algorithm also applies to answering queries in theories using the Closed-World Assumption and its generalizations. Similarly, since prioritized circumscription is equivalent to a conjunction of (parallel) circumscriptions, the algorithm can be used to answer queries in theories circumscribed by prioritized circumscription.