Pushdown Processes: Parallel Composition and Model Checking

In this paper, we consider a strict generalization of context-free processes, the pushdown processes, which are particularly interesting for three reasons: First, in contrast to context-free processes that do not support the construction of distributed systems, they are closed under parallel composition with finite state systems. Second, they are the smallest extension of context-free processes allowing parallel composition with finite state processes. Third, they can be model checked by means of an elegant adaptation to pushdown automata of the second order model checker introduced in [BuS92]. As arbitrary parallel composition between context-free processes provides Turing power, and therefore destroys every hope for automatic verification, pushdown processes can be considered as the appropriate generalization of context-free processes for frameworks for automatic verification.