PIERRE L. DOUILLET is an Associate Professor in Applicable Mathematics at the Ecole Nationale Superieure des Arts et Industries Textiles (Textile Engineers Institute), Roubaix, France. He studied Mathematics and Computer Science at the Ecole Normale Superieure (ENS Cachan, 1969-1974) and received his M.Sc and Ph.D. degrees in Computer Science from the Science University of Paris (Jussieu, Paris VI). His research interests include formal computing, approximations, network performances evaluation, operations research and computer's security. His email address is <douillet@ensait.fr> and his web page is http://www.douillet.info<www.douillet.info>