Hierarchical Automata and P-systems

In the context of a compositional theory of automata [8] (CP automata) we define a notion of hierarchical automaton, and show how the P-systems of Gh. Păun [9] may be described in terms of these automata. A distributive law for CP automata is proved which relates two different views of hierarchical systems: the first view is that hierarchical systems consist of layers, with communication between adjacent layers; the second is that a hierarchical system is an evolving hierarchy or tree structure.