DFT and belief revision

alchourrón devoted his last years to the analysis of the notion of defeasible conditionalization. he developed a formal system capturing the essentials of this notion. his definition of the defeasible conditional is given in terms of strict implication operator and a modal operator f which is interpreted as a revision function at the language level. in this paper, we will point out that this underlying revision function is more general than the well known agm revision [4]. in addition, we will give a complete characterization of that more general kind of revision and will show how permits to unify models of revision given by other authors.