 Dynamic doxastic logic (DDL) was introduced by Krister Segerberg to represent an agent who has opinions about the external world and changes these opinions upon receipt of new information. DDL makes use of epistemic modal operators of the type introduced by Hintikka (1962). The sentence \(B_i p\) denotes that the individual \(i\) believes that \(p\). When only one agent is under consideration, the subscript can be deleted, and the operator \(B\) can be read “it is believed that” or “the agent believes that” (Segerberg 1995, p. 536). 