Finite automata with undirected state graphs

Abstract We investigate finite automata whose state graphs are undirected. This means that for any transition from p to q consuming some letter a the input there exists symmetric as well. So, corresponding language families subregular, and in particular deterministic case, subreversible. In detail, we study operational descriptional complexity of nondeterministic undirected automata. To this end, different types on alphabets with few letters characterized. Then, Boolean operations well concatenation iteration is investigated, where tight upper lower bounds derived unary arbitrary under condition classes closed operation considered.