On Varieties of Literally Idempotent Languages

A language L A is literally idempotent in case that ua2 v L if and only if uav L, for each u, v A , a A. Varieties of literally idempotent languages result naturally by taking all literally idempotent languages in a classical (positive) variety or by considering a certain closure operator on classes of languages. We initiate the systematic study of such varieties. Various classes of literally idempotent languages can be characterized using syntactic methods. A starting example is the class of all finite unions of B 1 B 2 . . . B k where B1, . . . , Bk are subsets of a given alphabet A. 1991 Mathematics Subject Classification. 68Q45.

• Type: Journal
• Year: 2008
• Where: ITA
• Authors: Ondrej Klíma, Libor Polák
• Keywords: Certain Closure Operator, Communications, Idempotent Languages, ITA 2008, Systematic Study