Epistemic logic and logical omniscience II: A unifying framework

Ž In a published paper entitled Epistemic Logic and Logical Omniscience: A Survey Int J . Intell Syst 1997, 12, 57]81 a collection of epistemic logics were reviewed and critiqued. This sequel paper provides evidence for the claim that a unifying framework for various existing epistemic logics can be defined. Of particular interest is the logic of implicit and explicit belief, the logic of awareness, and the Cadoli]Schaerf epistemic model. Although these logics appear to have surface dissimilarities, a closer examination shows that they have a strong resemblance. The contribution of this paper is to show that a unifying Ž . framework MEL multi-̈ alued epistemic logic that integrates the features of these three logics can be defined. In this paper, it is proven that the semantics of MEL subsumes the semantics of the logic of implicit and explicit belief, the logic of awareness, and the Cadoli]Schaerf epistemic model. By placing some constraints on MEL, various epistemic notions such as implicit belief, explicit belief, and awareness can be modeled. Q 2000 John Wiley & Sons, Inc.