This book constitutes the refereed proceedings of the 4th International Conference on Algebraic
Informatics CAI 2011 held in Linz Austria in June 2011. The 12 revised full papers
presented together with 4 invited articles were carefully reviewed and selected from numerous
submissions. The papers cover topics such as algebraic semantics on graph and trees formal
power series syntactic objects algebraic picture processing finite and infinite computations
acceptors and transducers for strings trees graphs arrays etc. decision problems algebraic
characterization of logical theories process algebra algebraic algorithms algebraic coding
theory and algebraic aspects of cryptography.
