To Be Announced

In this survey we review dynamic epistemic logics with modalities for quantification over information change. Of such logics we present complete axiomatizations, focussing on axioms involving the interaction between knowledge and such quantifiers, we report on their relative expressivity, on decidability and on the complexity of model checking and satisfiability, and on applications. We focus on open problems and new directions for research

Asynchronous Announcements

We propose a multi-agent epistemic logic of asynchronous announcements, where truthful announcements are publicly sent but individually received by agents, and in the order in which they were sent. Additional to epistemic modalities the logic contains dynamic modalities for making announcements and for receiving them. What an agent believes is a function of her initial uncertainty and of the announcements she has received. Beliefs need not be truthful, because announcements already made may not yet have been received. As announcements are true when sent, certain message sequences can be ruled out, just like inconsistent cuts in distributed computing. We provide a complete axiomatization for this \emph{asynchronous announcement logic} (AA). It is a reduction system that also demonstrates that any formula in $AA$ is equivalent to one without dynamic modalities, just as for public announcement logic. The model checking complexity is in PSPACE. A detailed example modelling message exchanging processes in distributed computing in $AA$ closes our investigation

Hidden protocols: Modifying our expectations in an evolving world

When agents know a protocol, this leads them to have expectations about future observations. Agents can update their knowledge by matching their actual observations with the expected ones. They eliminate states where they do not match. In this paper, we study how agents perceive protocols that are not commonly known, and propose a semantics-driven logical framework to reason about knowledge in such scenarios. In particular, we introduce the notion of epistemic expectation models and a propositional dynamic logic-style epistemic logic for reasoning about knowledge via matching agentsÊ expectations to their observations. It is shown how epistemic expectation models can be obtained from epistemic protocols. Furthermore, a characterization is presented of the effective equivalence of epistemic protocols. We introduce a new logic that incorporates updates of protocols and that can model reasoning about knowledge and observations. Finally, the framework is extended to incorporate fact-changing actions, and a worked-out example is given. © 2013 Elsevier B.V

What will they say?—Public Announcement Games

Dynamic epistemic logic describes the possible information-changingactions available to individual agents, and their knowledge pre- and post conditions.For example, public announcement logic describes actions in the form of public,truthful announcements. However, little research so far has considered describing andanalysing rational choice between such actions, i.e., predictingwhat rational self-interestedagents actually will or should do. Since the outcome of information exchangeultimately depends on the actions chosen by all the agents in the system, and assumingthat agents have preferences over such outcomes, this is a game theoretic scenario.This is, in our opinion, an interesting general research direction, combining logic andgame theory in the study of rational information exchange. In this article we take somefirst steps in this direction: we consider the case where available actions are publicannouncements, and where each agent has a (typically epistemic) goal formula thatshe would like to become true. What will each agent announce? The truth of the goalformula also depends on the announcements made by other agents. We analyse suchpublic announcement games