#conditional-doxastic-models #doxastic-logic #logic-of-conditional-beliefs #private-announcements #public-announcements #serious-possibility-paradox-project
A knowledge-belief frame (KB-frame for short, see e.g. [17], pg. 89) is a Kripke frame of the form (S, → a , ∼ a ) a∈A , with a given set of states S and two binary relations for each agent; the first relation ∼ a is meant to capture the knowledge of agent a, while the second → a captures his beliefs. A KB frame is required to satisfy the following natural conditions: (1) each ∼ a is reflexive: s ∼ a s; (2) if s ∼ a t then we have: s → a w iff t → a w, and also s ∼ a w iff t ∼ a w; (3) if s → a t then s ∼ a t ; (4) for every s ∈ S there e xists some t ∈ S such that s → a t.