ON THE STRUCTURE OF FINITELY GENERATED SEMIGROUPS OF UNARY REGULAR LANGUAGES
Sergey Alexandrovich Afonin, Elena Khazova · International Journal of Foundations of Computer Science · 2010
The set of all regular languages is closed under concatenation and forms a monoid known as the monoid of regular languages. In this paper the structure of finitely generated subsemigroups of this monoid in case of one letter alphabet is investigated. We prove that finitely generated semigroups of regular languages over a one letter alphabet are Kleene, rational and thus automatic. It is already known that not all of finitely generated commutative semigroups are automatic, thus we may conclude that semigroups of unary regular languages have more rigid structure.