 The lack of a representation of conditional beliefs is closely connected to another limitation of the AGM system: its inability to model repeated or iterated belief revision. The input to a belief change is an epistemic state, consisting both of a set of propositions believed and an entrenchment relation on that set. The output of an AGM revision, in contrast, consists simply of a set of beliefs. The system provides no guidance on the question of what would be the result of revising an epistemic state in two or more steps. If the entrenchment relation could be explicitly represented by means of conditional propositions, then it would be possible to define the new entrenchment relation that would result from a single belief revision, making iterated belief revision representable. A number of proposals along these lines have been made. The difficulty lies in defining exactly what would constitute a minimal change in the relative entrenchment or epistemic ranking of a set of beliefs. To this point, no clear consensus has emerged on this question. (See Spohn 1988; Nayak 1994; Wobcke 1995; Bochman 2001.)