This volume is dedicated to Professor Arto Salomaa on the occasion of his 60th birthday. The volume reflects the broad spectrum of Professor Salomaa's research interests in theoretical computer science and mathematics with contributions particularly to automata theory, formal language theory, mathematical logic, computability, and cryptography.

Generalizing Cook's transformation to imperative stack programs.- A rewriting of Fife's theorem about overlap-free words.- Reconsidering the jeep problem or how to transport a birthday present to Salosauna.- Learning picture sets from examples.- Randomness as an invariant for number representations.- Cooperating grammars' systems: Power and parameters.- Parallel pattern generation with one-way communications.- Dynamic labeled 2-structures with variable domains.- Deciding the NTS property of context-free grammars.- Homomorphic representations by products of tree automata.- Identities and transductions.- Decomposition of infinite labeled 2-structures.- An iteration property of Lindenmayerian power series.- Comparing descriptional and computational complexity of infinite words.- On some open problems concerning the complexity of cellular arrays.- Power of controlled insertion and deletion.- From colonies to eco(grammar)systems.- On the multiplicity equivalence problem for context-free grammars.- On general solution of word equations.- On (left) partial shuffle.- Learning theoretical aspects is important but (Sometimes) dangerous.- Bisimulation, games, and logic.- Cryptographic protocols and voting.- Cryptographic protocols for auctions and bargaining.- On the size of components of cooperating grammar systems.- An elementary algorithmic problem from an advanced standpoint.- Event detection for ODES and nonrecursive hierarchies.- Rediscovering pushdown machines.- String matching algorithms and automata.- Classifying regular languages by their syntactic algebras.- On polynomial matrix equations XT=p(X) and X=p(X) Where all parameters are nonnegative.- Gram's equation — A probabilistic proof.