Recognisable Languages over Monads -- Garside and quadratic normalisation: a survey -- Grammar-Based Tree Compression -- On decidability of intermediate levels of concatenation hierarchies -- Ergodic in Finite permutations of minimal complexity -- Diverse Palindromic Factorization is NP-Complete -- Factorization in Formal Languages -- Consensus Game Acceptors -- On the Size of Two-Way Reasonable Automata for the Liveness Problem -- Squareable Words -- Complexity Analysis: Transformation Monoids of Finite Automata -- Palindromic complexity of trees -- Deciding proper conjugacy of classes of one-sided Finite-type-Dyck shifts -- Transfinite Lyndon words -- Unary patterns under permutations -- Finite Automata Over In Finite Alphabets: Two Models with Transitions for Local Change -- Enumeration formulin neutral sets -- On the Density of Context-Free and Counter Languages -- Star-Continuous Kleene Omega-Algebras -- Unary probabilistic and quantum automata on promise problems -- Generalizations of Code Languages with Marginal Errors -- Minimal Reversible Deterministic Finite Automata -- Multi-Sequential Word Relations -- The Boundary of Prefix-Free Languages -- A connected 3-state reversible Mealy automaton cannot generate an infinite Burnside group -- Path Checking for MTL and TPTL over Data Words -- On Distinguishing NC1 and NL -- Sur minimisation of automata -- On the Complexity of k-Piecewise Testability and the Depth of Automata -- Interval Exchange Words and the Question of Hof, Knill, and Simon -- State Complexity of Neighbourhoods and Approximate Pattern Matching -- Deterministic ordered restarting automata that compute functions -- Weight Assignment Logic -- Complexity Bounds of Constant-Space Quantum Computation.

This book constitutes the proceedings of the 19th International Conference on Developments in Language Theory, DLT 2015, held in Liverpool, UK. The 31 papers presented together with 5 invited talks were carefully reviewed and selected from 54 submissions. Its scope is very general and includes, among others, the following topics and areas: combinatorial and algebraic properties of words and languages, grammars, acceptors and transducers for strings, trees, graphs, arrays, algebraic theories for automata and languages, codes, efficient text algorithms, symbolic dynamics, decision problems, relationships to complexity theory and logic, picture description and analysis, polyominoes and bidimensional patterns, cryptography, concurrency, cellular automata, bio-inspired computing, and quantum computing.