Decidable and Undecidable Questions About Automata
John E. Hopcroft, Jeffrey David Ullman · Journal of the ACM · 1968
Four types of balloon automata (defined by one- or two-way input and deterministic or nondeterministic finite control) and closed classes of balloon automata were previously defined by the authors. A set of closed classes, one for each of the four types, is called a family if the classes use their infinite storage in the same way. The recursiveness and solvability of the emptiness problem for closed classes are investigated in the present paper. It is shown that in many cases the solvability of one of these questions for one closed class in a family implies that some other question are solvable for the closed classes of that family.