Affiliation: | (1) ELCA Informatique SA, Ave de la Harpe 22-24, Case Postale 519, CH-1001 Lausanne, Switzerland;(2) Department of Computer Science, University of Houston, 4800 Calhoun Rd., Houston, TX 77204-3010, USA;(3) LIACC / Faculty of Economics, University of Porto, R. Campo Alegre, 823, 4150-180 Porto, Portugal |