Joseph Y. Halpern

Professor
Co-director: Cognitive Studies Program
halpern@cs.cornell.edu
http://www.cs.cornell.edu/home/halpern/
Ph.D. Harvard University, 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 each of these areas as well.

Some themes of my current research include: (1) applying ideas of decision theory to constructing algorithms in asynchronous distributed systems, database systems, and wireless systems; (2) providing foundations for useful qualitative notions of decision theory; (3) reasoning about security.

Honors

Milner Lecturer at the University of Edinburgh, May 2000.

University Activities Co-director: Cognitive Studies Program.

Professional Activities Fellow: American Association of Artificial Intelligence.

Editor-in-chief: Journal of the ACM (as of May, 1997).

Consulting Editor: Chicago Journal of Computer Science.

Editorial Board Member: Artificial Intelligence Journal; Information and Computation; Journal of Logic and Computation.

Member: ACM Publications Board; LICS (IEEE Conference on Logic in Computer Science)
Advisory Board.

Chairman: ACM Preprint Repository.

Coordinator: CoRR (Computing Research Repository).

President of Board of Directors: Corporation for Theoretical Aspects of Reasoning About Knowledge.

Program Committee Member: 16th Annual Conference on Uncertainty in Artificial Intelligence.

Lectures

Plausibility measures and default reasoning. Invited lecture. 14th Annual IEEE Conference on Logic in Computer Science, July 1999.

—. Invited lecture. Edinburgh University, May 2000.

Reasoning about common knowledge with infinitely many agents. IEEE Symposium on Logic in Computer Science, July 1999.

Probability update: conditioning vs. cross-entropy. Invited lecture. IBM Almaden Research Center, August 1999.

—. Invited lecture. Edinburgh University, May 2000.

The Computing Research Repository: promoting the rapid dissemination and archiving of computer science. ACM Digital Libraries ’99, August 1999.

Using multi-agent systems to represent uncertainty. University of Delaware Fall Computer Science Colloquium, October 1999.

Reasoning about knowledge. Milner Lecture. Edinburgh University, May 2000.

Causes and explanations: a structural-model approach. Department of Philosophy, Cornell University, March 2000.

A computer scientist looks at game theory. Department of Economics, Cornell University, May 2000.

Publications

“Belief revision: a critique.” Journal of Logic, Language, and Information 8 (1999), 401–420 (with N. Friedman).

“Hypothetical knowledge and counterfactual reasoning.” International Journal of Game Theory 28:3 (1999), 315–330.

“The hierarchical approach to modeling knowledge and common knowledge.” International Journal of Game Theory 28:3 (1999), 331–365 (with R. Fagin, J. Geanakoplos, and M. Y. Vardi).

“Reasoning about noisy sensors in the situation calculus.” Artificial Intelligence 111(1999), 171–208 (with F. Bacchus and H.J. Levesque).

“Set-theoretic completeness for epistemic and conditional logic.” Annals of Mathematics and Artificial Intelligence 26 (1999), 1–27.

“Cox’s Theorem revisited.” Journal of AI Research 11 (1999), 429–435.

“Reasoning about common knowledge with infinitely many agents.” Proceedings of the 14th IEEE Symposium on Logic in Computer Science (July 1999), 384–393 (with R. Shore).

“A logic for SDSI’s linked local named spaces.” Proceedings of the 12th IEEE Computer Security Foundations Workshop (July, 1999), 111–122 (with R. van der Meyden).

“The Computing Research Repository: promoting the rapid dissemination and archiving of computer science.” Proceedings of ACM Digital Libraries ’99 (August 1999), 3-11 (with C. Lagoze).

“Plausibility measures and default reasoning: an overview (summary of invited talk).” Proceedings of the 14th IEEE Symposium on Logic in Computer Science (July 1999), 130–135 (with N. Friedman).

“Editorial: Taking stock.” Journal of the ACM 46, 3 (1999), 323–324.