Generalizations of Checking Stack Automata: Characterizations and Hierarchies

We examine different generalizations of checking stack automata (e.g., allowing multiple input heads and multiple stacks) and characterize their computing power in terms of two-way multi-head finite automata and space-bounded Turing machines. For various models, we obtain hierarchies in terms of their computing power. Our characterizations and hierarchies expand or tighten some previously known results.