Syntactic Update

We present an update operation, syntactic update, based on Winslett's Possible Models Approach (PMA). The PMA receives a set of propositional formulas describing a situation of the world, and a set of formulas describing the postconditions of an action, and determines the set of models describing the possible states of the world after the execution of the action. In this paper we describe a way of getting from the set of models of the PMA, back to a set of formulas which is as similar as possible to the initial set.