Advances in Dynamic Epistemic Logic

The paper fixes a formalization of dynamic epistemic logic, loosely based on Baltag, Moss, Solecki [1], and proves a number of useful facts about epistemic update logic. In particular, the notion of an action emulation is proposed as a notion of equivalence more appropriate for action models than bisimulation. It is proved that every bisimulation is an action emulation, but not vice versa, and that action models that effect the same updates are the same modulo action emulation. Next, some results are proved about the effects of communicative actions, and further questions are put on the research agenda.