Distance semantics for belief revision

A vast and interesting family of natural semantics for belief revision is d efined. Suppose one is given a distance d between any two models. One may t hen define the revision of a theory K by a formula a as the theory defined by the set of all those models of alpha that are closest, by d, to the set of models of K. This Family is characterized by a set of rationality postul ates that extends the AGM postulates. The new postulates describe propertie s of iterated revisions.