main.h10.gif (24830 bytes) Joseph Y. Halpern
Professor
Co-director, Cognitive Studies Program
halpern@cs.cornell.edu
www.cs.cornell.edu/home/halpern/home.html
Ph.D. Harvard, 1981

 My research is concerned with representing and reasoning about knowledge and uncertainty in multi-agent systems. The work uses tools from logic (particularly modal logic and the idea of possible-worlds semantics), probability theory, distributed systems, game theory, and AI, and I like to think that it contributes to our understanding of these areas as well.

 Some themes of my current research include: (1) defining useful notions of explanation in probabilistic systems, (2) providing foundations for useful qualitative notions of decision theory, and (3) applying ideas of decision theory to constructing algorithms in asynchronous distributed systems.

Awards

 1997 Gödel Prize

University Activities

Co-director: Cognitive Studies Program 

Professional Activities

Fellow: American Association of Artificial Intelligence
Editor-in-chief: Journal of the ACM
Consulting Editor: Chicago Journal of Computer Science
Editorial Board: Artificial Intelligence Journal, Information and Computation, Journal of Logic and Computation
Member: ACM Publications Board; Head of steering committee to set up ACM Preprint Server
Program Committee Member: 13th Annual Conference on Uncertainty in Artificial Intelligence, International Conference on Temporal Logic
Conference Chair: 7th Conference on Theoretical Aspects of Rationality and Knowledge
President of Board of Directors: Corporation for Theoretical Aspects of Reasoning About Knowledge
NSF Review Panel

Lectures

Representation independence in proba-bilistic reasoning. ISP, Pittsburgh University, Pittsburgh, PA, May 1997.
Reasoning about knowledge in multi-agent systems. Computer Science, Indiana University, Bloomington, IN, May 1997.
____. Computer Science, Washington University, St. Louis, MI, May 1997.
On ambiguities in the interpretation of game trees. Economics, Cornell University, Ithaca, NY, May 1997.
From statistics to beliefs. Philosophy, Carnegie-Mellon University, Pittsburgh, PA, May 1997.
Using multi-agent systems to represent uncertainty. IRCS, University of Pennsylvania, Philadelphia, PA, March 1997.
Reasoning about knowledge in multi-agent systems. Economics, University of Pennsylvania, Philadelphia, PA, March 1997.
On ambiguities in the interpretation of game trees. SITE 96 Workshop on Game Theory, Stanford University, Palo Alto, CA, 1996.
Belief revision: a critique, 5th International Conference on Principles of Knowledge Representation and Reasoning (KR '96), Boston, MA, November 1996.
Reasoning about knowledge in multi-agent systems. Economics Department, Cornell University, Ithaca, NY, September 1996.
Using multi-agent systems to represent uncertainty. Invited talk. AAAI '96 (Thirteenth National Conference on Artificial Intelligence), Portland, August 1996.
A counterexample to theorems of Cox and Fine, AAAI '96 (Thirteenth National Conference Artificial Intelligence), Portland, Pittsburgh, PA, August 1996.
Defining relative likelihood in partially-ordered preferential structures, Twelfth Conference on Uncertainty in AI, Portland, OR, August 1996.

Publications

 A critical reexamination of autoepistemic logic, default logic, and only knowing. Computational Intelligence, 13:1, pp. 144-163, February 1997.
A theory of knowledge and ignorance for many agents. Journal of Logic and Computation, 7:1, pp. 79-108, January 1997.
Belief revision: A critique. Proceedings 5th International Conference on Principles of Knowledge Representation and Reasoning KR '96, pp. 421-431, November 1996. (With N. Friedman.)
From statistical knowledge bases to degrees of belief. Artificial Intelligence, 87:1-2, pp. 75-143, October 1996. (With F. Bacchus, A. J. Grove, and D. Koller.)
Should knowledge entail belief? Journal of Philosophical Logic, 25:5, pp. 483-494, October 1996.
Common knowledge: now you have it, now you don't. Intelligent Systems: A Semiotics Perspective, Proceedings International Multidisciplinary Conference, Vol. 1, pp. 177-183, October 1996. (With R. Fagin, Y. Moses, M. Vardi.)
A counterexample to theorems of Cox and Fine. AAAI-96 Proceedings Thirteenth National Conference on Artificial Intelligence, pp. 1313-1319, August 1996.
Plausibility measures and default reasoning. AAAI-96 (Proceedings Thirteenth National Conference on Artificial Intelligence, pp. 1297-1304, August 1996. (With N. Friedman.)
Using multi-agent systems to represent uncertainty. Summary of invited talk, AAAI-96 Proceedings Thirteenth National Conference on Artificial Intelligence, pp. 1329-1330, August 1996.
Irrelevance and conditioning in first-order probabilistic logic. AAAI-96 (Proceedings Thirteenth National Conference on Artificial Intelligence, pp. 569-576, August 1996. (With D. Koller.)
First-order conditional logic revisited. AAAI-96 Proceedings Thirteenth National Conference on Artificial Intelligence, pp. 1305-1312, August 1996. (With N. Friedman and D. Koller.)
Defining relative likelihood in partially-ordered preferential structures. Proceedings Twelfth Conference on Uncertainty in AI, pp. 299-306, August 1996.
A qualitative Markov assumption and its implications for belief change. Proceedings Twelfth Conference on Uncertainty in AI, pp. 263-273, August 1996. (With N. Friedman.)