Krzysztof R. Apt received his PhD in 1974 in mathematical logic from the University of Warsaw in Poland. He is a senior researcher at CWI, Amsterdam and Professor of Computer Science at the University of Amsterdam. He is the author of three other books: Verification of Sequential and Concurrent Programs (with E.-R. Olderog), From Logic Programming to Prolog, and Principles of Constraint Programming, and has published 50 journal articles and 15 book chapters. He is the founder and the first editor-in-chief of the ACM Transactions on Computational Logic, and past president of the Association for Logic Programming. He is a member of the Academia Europaea (Mathematics and Informatics Section). After completing a degree at Oxford in Mathematics and Philosophy, Mark Wallace joined the UK computer company ICL, who funded his PhD at Southampton University, and which was published as a book: Communicating with Databases in Natural Language. He has been involved in the ECLiPSe constraint programming language since its inception and has led several industrial research collaborations exploiting the power of constraint programming with ECLiPSe. He is currently involved in a major new constraint programming initiative funded by National ICT Australia (NICTA), and in the foundation of a Centre for Optimisation in Melbourne. He has published widely, chaired the annual constraint programming conference, and is an editor for three international journals.