th This Festschrift is dedicated to Christoph Walther on the occasion of his 60 th birthday on August 9, 2010. It consists of articles by some of his colleagues and former students, who, on this momentous occasion, chose to show their appreciation. Inteachingtheoreticalcomputerscience, Christophhas hadaprofoundin- ence onmany ofhis formerandcurrentstudents, notleastby the introductionof eriFun into the classroom. Outside of his teaching, developing eriFun played a major role in his recent research activities. When the idea for this Festschrift was ?rst presented to us, it quickly - came...