Applicable algebra and artificial intelligence

In February 2008, a workshop Applicable Algebra and Computer Science was organised by us in Logroño (Spain) in order to honour Jacques Calmet on the occasion of his retirement at Karlsruhe University in the winter term 2007.1 In the wake of the workshop, the idea of this special issue on the slightly more specialised topic Applicable Algebra and Artificial Intelligence was born (kindly suggested by Martin Golumbic, Editor-in-chief of the journal Annals of Mathematics and Artificial Intelligence). Some authors were specifically invited to submit an article; others answered an open call for papers. All submissions were refereed according to the usual standards of AMAI by at least two independent referees (leading to the rejection of several manuscripts). However, before we briefly discuss the contents of this special issue, we must say a few words about Jacques Calmet and his work. Jacques started his career as a theoretical physicist obtaining his Ph.D. at the University of Marseille in 1970. Already at that time he was interested in what is nowadays called computer algebra and developed LISP programs for calculations with Feynman diagrams.2 Around 1979, Jacques decided to leave physics and to move to computer science. At the same time, he also moved to the University of