Special Session LIRa Seminar on Messages, Information and Norms in Utrecht

(slides | handout on the Gibbard/Satterthwaite Theorem)

A message is an item with a sender, a body of information, and a set of recipients, where the body of information can quote other messages. We will present a system for message passing (syntax plus semantics), discuss its logic, sketch some applications, and generate a list of open questions.  Background assumptions are that message senders are honest, and that the network is reliable. (joint work with Floor Sietsma)

In epistemic logic, multi-agent Kripke structures are used to model the distribution of information in a system. In this talk, I present an approach to quantifying how the information is distributed among the different agents, or how important each agent is, with respect to some fact represented as a goal formula. It is typically the case that the goal formula is distributed knowledge in the system, but that no individual agent alone knows it. It might be that several different groups of agents can get to know the goal formula together by combining their individual knowledge. I will argue that voting games and power indices such as the Banzhaf index, developed in game theory and voting theory, are useful for analysing such scenarios. These information-based power indices can be expressed in standard epistemic logic which allows, e.g., standard tools to be used to quantitatively analyse the distribution of information in a given Kripke structure. (joint work with Wiebe van der Hoek and Michael Wooldridge)

The environment is an essential component of multi-agent systems, which is often used to coordinate the behaviour of individual agents. Recently many programming languages have been proposed to facilitate the implementation of such environments. This paper is motivated by a programming language that is designed to implement environments in terms of normative concepts such as norms and sanctions. We provide a formal analysis of programmed normative environments from a mechanism design perspective. By doing this we relate normative environment programs to mechanism design, setting the stage for studying formal properties of normative environment programs such as whether a set of norms implements a specific choice function in a specific equilibria.