Variants of codes and indecomposable languages
We continue the investigation of representing a language as a catenation of languages, each of which cannot be further decomposed in a nontrivial fashion. We study such prime decompositions, both finite and infinite ones. The notion of a length code, an extension of the notion of a code leads to general results concerning decompositions of star languages. Special emphasis is on the decomposition of regular languages. Also some open problems are mentioned. (C) 2009 Elsevier Inc. All rights reserved.
language catenation of languages prime decomposition decomposition length code star language