Institution: | Université Louis Pasteur, 7 rue René Descartes, 67084 Strasbourg Cedex, France ; Department of Computer Science, Kossuth Lajos University, P.O. Box 12, H-4010 Debrecen, Hungary ; FB-14 Informatik, Universität des Saarlandes, Postfach 151150, D-66041 Saar- brücken, Germany |