TARK XII took take place at Stanford University on July 6 - 8, 2009. The mission of the TARK conferences is to bring together researchers from a wide variety of fields, including Artificial Intelligence, Cryptography, Distributed Computing, Economics and Game Theory, Linguistics, Philosophy, and Psychology, in order to further our understanding of interdisciplinary issues involving reasoning about rationality and knowledge. Topics of interest include, but are not limited to, semantic models for knowledge, belief, and uncertainty, bounded rationality and resource-bounded reasoning, commonsense epistemic reasoning, epistemic logic, knowledge and action, applications of reasoning about knowledge and other mental states, belief revision, and foundations of multi-agent systems.

TARK XII will have a partial overlap with the Tenth ACM Conference on Electronic Commerce (EC'09) at Stanford University