The theory of formal languages is widely recognized as the backbone of theoretical computer science, originating from mathematics and generative linguistics, among others. As a foundational discipline, formal language theory concepts and techniques are present in a variety of theoretical and applied fields of contemporary research which are concerned with symbol manipulation: discrete mathematics, bioinformatics, natural language processing, pattern recognition, text retrieval, learning, cryptography, compression, etc. This volume presents the main results of some recent, quickly developing...