Restricted Towers of Hanoi and Morphisms -- Collapsing Words: A Progress Report -- Locally Consistent Parsing and Applications to Approximate String Comparisons -- Central Sturmian Words: Recent Developments -- Reversible Cellular Automata -- Inexpressibility Results for Regular Languages in Nonregular Settings -- Complexity of Quantum Uniform and Nonuniform Automata -- Membership and Finiteness Problems for Rational Sets of Regular Languages -- Tissue P Systems with Antiport Rules and Small Numbers of Symbols and Cells -- The Mortality Threshold for Partially Monotonic Automata -- Sturmian Words: Dynamical Systems and Derivated Words -- Schützenberger and Eilenberg Theorems for Words on Linear Orderings -- On the Membership of Invertible Diagonal Matrices -- A Kleene Theorem for Languages of Words Indexed by Linear Orderings -- Revolving-Input Finite Automata -- Some New Results on Palindromic Factors of Billiard Words -- A Note on a Result of Daurat and Nivat -- Palindromes in Sturmian Words -- Voronoi Cells of Beta-Integers -- Languages with Mismatches and an Application to Approximate Indexing -- Bidimensional Sturmian Sequences and Substitutions -- Unambiguous Morphic Images of Strings -- Complementing Two-Way Finite Automata -- On Timed Automata with Discrete Time – Structural and Language Theoretical Characterization -- Monotone Deterministic RL-Automata Don’t Need Auxiliary Symbols -- On Hairpin-Free Words and Languages -- Adding Monotonic Counters to Automata and Transition Graphs -- Polynomial Generators of Recursively Enumerable Languages -- On Language Inequalities XK???LX -- The Power of Tree Series Transducers of Type I and II -- The Inclusion Problem for Unambiguous Rational Trace Languages -- LR Parsing for Boolean Grammars -- On Some Properties of the Language of 2-Collapsing Words -- Semi-rational Sets of DAGs -- On the Frequency of Letters in Pure Binary Morphic Sequences.

This book constitutes the refereed proceedings of the 9th International Conference on Developments in Language Theory, DLT 2005, held in Palermo, Italy in July 2005. The 29 revised full papers presented together with 5 invited papers were carefully reviewed and selected from 73 submissions. All important issues in language theory are addressed including grammars, acceptors, and transducers for strings frees, graphs, and arrays; efficient text algorithms; algebraic theories for automata and languages; variable-length codes; symbolic dynamics; decision problems; relations to complexity theory and logic; picture description and analysis; cryptography; concurrency; DNA computing; and quantum computing.