 Descriptor revision (Hansson 2017) is based on two major formal constructions. One of them is a metalinguistic belief predicate \(\mathfrak{B}\) that is applied to sentences of the object language. \(\mathfrak{B}p\) denotes that the sentence \(p\) is believed, \(\neg \mathfrak{B}p\) that it is not believed, and \(\mathfrak{B}p\vee \mathfrak{B}q\) that either \(p\) or \(q\) is believed. Such sentences can be used to express the success conditions of belief change operations. Thus \(\mathfrak{B}p\) is the success condition of revision by \(p\), \(\neg \mathfrak{B}p\) that of contraction by \(p\) and \(\{\neg \mathfrak{B}p,\neg \mathfrak{B}q\}\) that of multiple contraction by \(\{p,q\}\). Due to the versatility of descriptors we only need one operation, denoted \(\circ\). Hence, \(K\circ \mathfrak{B}p\) represents revision by \(p\) and \(K \circ \neg \mathfrak{B}p\) contraction by \(p\). 