Dynamic consequence and public announcement

Junta de Andalucía P08-HUM- 04159European Research Council EPS 313360

Epistemic protocols for dynamic gossip

A gossip protocol is a procedure for spreading secrets among a group of agents, using a connection graph. In each call between a pair of connected agents, the two agents share all the secrets they have learnt. In dynamic gossip problems, dynamic connection graphs are enabled by permitting agents to spread as well the telephone numbers of other agents they know. This paper characterizes different distributed epistemic protocols in terms of the (largest) class of graphs where each protocol is successful, i.e. where the protocol necessarily ends up with all agents knowing all secrets

What is my number? – A new epistemic riddle

Abstract. A common theme in epistemic riddles is that announcements of ignorance may eventually result in knowledge. We present a fairly new epistemic riddle, including some variants that were partly accidentally designed due to a miscommunication between logic puzzle enthusiasts. The design was facilitated because such riddles can be specified, and fairly easily checked, in ‘public announcement logic’, a modal logic with both dynamic and epistemic operators; and because of the availability of epistemic model checking tools for the finetuning and verification of results. Logic puzzle design could benefit from similar future efforts

The secret of My Success

In an information state where various agents have both factual knowledge and knowledge about each other, announcements can be made that change the state of information. Such informative announcements can have the curious property that they become false because they are announced. The most typical example of that is `fact p is true and you don't know that', after which you know that p,which entails the negation of the announcement formula. The announcement of such a formula in a given information state is called an unsuccessful update. A successful formula is a formula that always becomes common knowledge after being announced. Analysis of information systems and `philosophical puzzles' reveals a growing number of dynamic phenomena that can be described or explained by unsuccessful updates. This increases our understanding of such philosophical problems. We also investigate the syntactic characterization of the successful formulas