Epistemic properties of knowledge hierarchies

After proving correspondence theorems between syntactic and semantic proper ties of a Kripke Structure, these properties are combined in order to gener ate two polar semantic structures, that is, partitions and nestings. Then, the relevant properties are extended to Probabilistic Kripke Structures and the concept of a Mixed Knowledge Hierarchy is introduced and associated wi th two dual measures of events. Finally, an application to Decision Theory is provided for the particular case of a 2-level hierarchy. (C) 1999 Elsevi er Science S.A. All rights reserved.