Dois seminários do Prof. Joseph Halpern (Cornell University) na UFPE

[Gauss Cordeiro <gauss@de.ufpe.br>]

Data: 21/03/2013
Hora: 16h
Local: Anfiatro do Depto. de Eletrônica e Sistemas, 4o. andar do Bloco
Escolar do CTG

Título: "Weighted Sets of Probabilities and Minimax Weighted Expected
Regret: New Approaches for Representing Uncertainty and Making Decisions"

Resumo: "Suppose that an agent's uncertainty is represented by
a set of probability measures, rather than a single measure.
How should that the agent update her uncertainty when she acquires new
information?  The obvious approach, measure-by-measure updating,
is well-known to suffer from problems; agents are not always able
to learn appropriately.  To deal with these problems, we propose using
weighted sets of probabilities: a representation where each measure
is associated with a weight, which denotes its significance.
We describe a natural approach to updating in such a situation and a
natural approach to determining the weights.  We then show how
this representation can be used in decision-making, by modifying
a standard approach to decision making -- minimizing expected regret
-- to obtain minimax weighted expected regret (MWER).  We provide an
axiomatization that characterizes preferences induced by MWER
both in the static and dynamic case. This represents joint work with
Samantha Leung."

Data: 22/03/2013
Hora: 10h
Local: Anfiteatro do CIN.

Título: "Beyond Nash Equilibrium: Solution Concepts for the 21st Century"

Resumo: "Nash equilibrium is the most commonly-used notion of
equilibrium in game
theory.  However, it suffers from numerous problems.  Some are well known
in the game theory community; for example, the Nash equilibrium of repeated
prisoner's dilemma is neither normatively nor descriptively reasonable.
However, new problems arise when considering Nash equilibrium from a
computer science perspective: for example, Nash equilibrium is not robust
(it does not tolerate "faulty" or "unexpected" behavior), it does not
deal with coalitions, it does not take computation cost into account, and
it does not deal with cases where players are not aware of all aspects of
the game.  In this talk, I discuss solution concepts that try to address
these shortcomings of Nash equilibrium.  This talk represents joint work
with various collaborators, including Ittai Abraham, Danny Dolev, Rica
Gonen, Rafael Pass, and Leandro Rego.  No background in game theory will
be presumed."

Biografia: "Joseph Y. Halpern received a B.Sc. in mathematics from
the University of Toronto in 1975 and a Ph.D. in mathematics from
Harvard in 1981. He joined the IBM Almaden Research Center in 1982,
where he remained until 1996. He served as manager of the Mathematics
and Related Computer Science Department at IBM from 1988-1990 and was
a consulting professor at Stanford from 1984-1996. In 1996, he moved
to Cornell University, where he is a professor in Computer Science.

He has coauthored 5 patents, two books ("Reasoning About Knowledge"
and "Reasoning about Uncertainty"), and well over 100 journal
publications and 100 conference publications. He was designated Highly
Cited Researcher by the Institute for Scientific Information. Prof.
Halpern received the Publishers' Prize for Best Paper at the
International Joint Conference on Artificial Intelligence in 1985
(joint with Ronald Fagin) and in 1989, the 1997 Godel Prize (joint
with Yoram Moses), and two IBM Outstanding Innovation Awards. He is a
Fellow of AAAI (American Association of Artificial Intelligence), AAAS
(American Association for the Advancement of Science), and ACM
(Association for Computing Machinery). He was editor-in-chief of
Journal of the ACM, and currently serves on the editorial board of
Journal of Logic and Computation, Games and Economic Behavior, and
Artificial Intelligence."