Developments in Language Theory

Invited Papers.- Recognizable Sets of Graphs, Hypergraphs and Relational Structures: A Survey.- Some New Directions and Questions in Parameterized Complexity.- Basic Notions of Reaction Systems.- A Kleene Theorem for a Class of Communicating Automata with Effective Algorithms.- Algebraic and Topological Models for DNA Recombinant Processes.- Contributed Papers.- Regular Expressions for Two-Dimensional Languages Over One-Letter Alphabet.- On Competence in CD Grammar Systems.- The Dot-Depth and the Polynomial Hierarchy Correspond on the Delta Levels.- Input Reversals and Iterated Pushdown Automata: A New Characterization of Khabbaz Geometric Hierarchy of Languages.- On the Maximum Coefficients of Rational Formal Series in Commuting Variables.- On Codes Defined by Bio-operations.- Avoidable Sets and Well Quasi-Orders.- A Ciliate Bio-operation and Language Families.- Semantic Shuffle on and Deletion Along Trajectories.- Sturmian Graphs and a Conjecture of Moser.- P Systems Working inthe Sequential Mode on Arrays and Strings.- Optimal Time and Communication Solutions of Firing Squad Synchronization Problems on Square Arrays, Toruses and Rings.- The Power of Maximal Parallelism in P Systems.- An Efficient Pattern Matching Algorithm on a Subclass of Context Free Grammars.- On the Complexity of 2-Monotone Restarting Automata.- On Left-Monotone Deterministic Restarting Automata.- On the Computation Power of Finite Automata in Two-Dimensional Environments.- The Role of the Complementarity Relation in Watson-Crick Automata and Sticker Systems.- The Boolean Closure of Linear Context-Free Languages.- Context-Sensitive Decision Problems in Groups.- Decidability and Complexity in Automatic Monoids.- Relating Tree Series Transducers and Weighted Tree Automata.- An NP-Complete Fragment of LTL.- From Post Systems to the Reachability Problems for Matrix Semigroups and Multicounter Automata.- Words Avoiding -Powers and the Thue-Morse Morphism.- On the Equivalence Problem for