Hennessy-Milner Classes and Process Algebra

This paper studies Hennessy-Milner classes, classes of Kripke models where modal-logical equivalence coincides with bisimulation. Concepts associated with these classes in the literature (Goldblatt [6], Visser [8])are studied and compared and the structure of the collection of maximal Hennessy-Milner classes is investigated (how many are there, what is their intersection?). The insights into these classes are applied to process algebra. This results in a Hennessy-Milner process algebra for a non-trivial process language, whose standard graph-semantics is not Hennessy-Milner.