 Interest in epistemic logic extends well beyond philosophers. Recent decades have seen a great deal of interdisciplinary attention to epistemic logic with economists and computer scientists actively developing the field together with logicians and philosophers. In 1995 two important books signaled the fertile interplay between computer science and epistemic logic: Fagin, Halpern, Moses, and Vardi (1995) and Meyer and van der Hoek (1995). Work by computer scientists has become increasingly central to epistemic logic in the intervening years.