Bilocally testable languages. (English) Zbl 0553.68045

In the paper we present a characterization of bilocally testable languages i.e. the next family after locally testable languages in the finite-cofinite hierarchy of dot-depth one languages. This characterization shows that the concept of localization, which is true for local testability, fails in this case.


68Q45 Formal languages and automata
20M35 Semigroups in automata theory, linguistics, etc.