Research for formal languages have two main lines, automatons and formal grammars.A new line for formal languages, digraph languages is built.Furthermore,two special digraph languages,de Bruijn digraph languages and Kautz digraph languages are discussed.Two concepts, connected languages and diameter of languages are also proposed.The diameters of de Bruijn digraph languages and Kautz digraph languages are computed.
formal languagedigraphdigraph languagede Bruijn digraph languageKautz digraph language