The Chinese University of Hong Kong
Department of Computer Science and Engineering


Title: What Does a Group Know?
Date: February 4, 2016 (Thursday)
Time: 2:30 p.m. - 3:30 p.m.
Venue: Room 121, 1/F, Ho Sin-hang Engineering Building,
The Chinese University of Hong Kong,
Shatin, N.T.
Speaker: Professor Thomas Agotnes
Department of Information Science and Media Studies
University of Bergen, Norway



What do we mean when we say that a group knows something? Reasoning about knowledge is of importance in modeling and analyzing multi-agent systems and other distributed systems, and various notions of group knowledge have been proposed and shown to be useful. In my talk I will review these, argue that many of them are problematic, and propose some alternatives and extensions. The talk will be based on standard formalisations of knowledge and belief in modal logic. I will discuss a natural range of group belief concepts with distributed and general ("everybody-believes") as the two extreme endpoints and with many intermediate concepts in between. Distributed knowledge is sometimes described as what the members of the group would know of they "pool their knowledge together". This is inaccurate at best: for example, it is consistent that a group has distributed knowledge of a Moore sentence involving one of the members of the group (a sentence which cannot be known by that member, no matter how much "pooling" has taken place). I will also present and discuss a new group modality that actually captures what is true after the group have fully shared their information with each other -- after their distributed knowledge has been resolved.



Thomas Agotnes is a professor of information science at the University of Bergen, Norway, and a visiting professor at the Center of the study of Language and Cognition at Zhejiang University, China. Since his PhD in 2004 Agotnes has worked and published extensively in applied logic, multi-agent systems, artificial intelligence and related areas. A main focus is logic-based knowledge representation and reasoning, in particular formalising different forms of interaction. He is particularly interested in connections between mathematical models in the social sciences, e.g., in game theory, and formal logic. With co-authors Agotnes has been was awarded the best paper award at the AAMAS conference, the leading multi-agent systems conference. He is an active member of the international multi-agent systems community. Agotnes is a member of the board of directors of the European Association for Multi-Agent Systems (EURAMAS), was a PC chair of LOFT 2014 and DEON 2012, and the general chair of STAIRS 2010. He was an invited keynote speaker at SLS 2014, DALT 2012, JAWS 2011 and CLIMA 2010.


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