 The formula \(Bp\) in DDL differs from the expression \(p \in K\) of AGM in being a sentence in the same language as \(p\). This makes it possible to express in the object language that a sentence is believed. In this way, Segerberg attempted to develop belief revision “as a generalization of ordinary Hintikka type doxastic logic”, whereas in contrast “AGM is not really logic; it is a theory about theories” (Segerberg 1999, p. 136). In the DDL framework it is possible to express beliefs about beliefs. The sentence “\(i\) believes that \(i\) does not believe that \(p\)” can be expressed as \(B_i \neg B_i p\), whereas there is no way to express it in the AGM framework. \(((p \not\in K_i) \in K_i\) is not a well-formed formula.)