Uniform Distributed Pushdown Automata Systems

Abstract

A distributed pushdown automata system consists of several pushdown automata which work in turn on the input word placed on a common one-way input tape under protocols and strategies similar to those in which cooperating distributed (CD) grammar systems work. Unlike the CD grammar systems case, where one may add or remove duplicate components without modifying the generated language, the identical components play an important role in distributed pushdown automata systems. We consider here uniform distributed pushdown automata systems (UDPAS), namely distributed pushdown automata systems having all components identical pushdown automata. We consider here just a single protocol for activating/deactivating components, namely a component stays active as long as it can perform moves, as well as two ways of accepting the input word: by empty stacks (all components have empty stacks) or by final states (all components are in final states), when the input word is completely read. We mainly investigate the computational power of UDPAS accepting by empty stacks and a few decidability and closure properties of the families of languages they define. Some directions for further work and open problems are also discussed.