This book constitutes the refereed proceedings of the 15th International Conference on Rewriting Techniques and Applications, RTA 2004, held in Aachen, Germany in June 2004.

This Festschrift is dedicated to Jan Willem Klop on the occasion of his 60th birthdayon December 19,2005.Its focus is on the lambda calculus, term rewr- ing and process algebra, the ?elds where Jan Willem has made fundamental contributions. Without attempting to give a balanced account of Jan Willem s scienti?c achievements, we recall three accomplishments from the early years of his career that especially stand out. The ?rst is his counterexample showing that the extension of the lambda calculus with surjective pairing lacks the Church Rosserproperty, or, in modern terminology, is not...

A compilation of papers presented at the 1999 European Summer Meeting of the Association for Symbolic Logic, Logic Colloquium '99 includes surveys and research articles from some of the world's preeminent logicians. Two long articles are based on tutorials given at the meeting and present accessible expositions of current research in two active areas of logic, geometric model theory and descriptive set theory of group actions. The other articles cover current reseach topics in all areas of mathematical logic, including logic in computer science, proof theory, set theory, model theory,...

A compilation of papers presented at the 1999 European Summer Meeting of the Association for Symbolic Logic, Logic Colloquium '99 includes surveys and research articles from some of the world's preeminent logicians. Two long articles are based on tutorials given at the meeting and present accessible expositions of current research in two active areas of logic, geometric model theory and descriptive set theory of group actions. The other articles cover current reseach topics in all areas of mathematical logic, including logic in computer science, proof theory, set theory, model theory,...