Iterable AGM Functions
Carlos Areces, Verónica Becher

Abstract:
The AGM model has been criticized for not addressing the problem
of iterated change. This is true, but in some cases the invalid claim
that "AGM does not allow iteration" has been made. In this paper we
examine the most elementary scheme of iteration: an iterable function.
We formulate an iterable version of the AGM model, showing that
the AGM formalism is in fact compatible with iteration. Following
Alchourr\'on and Makinson's early reference to an iterable form of a
safe contraction function, we give an iterable construction for each
of the five AGM presentations (meet functions, systems of spheres,
postulates, epistemic entrenchments and safe hierarchies) and prove
their equivalence.