1. Department of Computer Science; Federal University Of Ceará; Fortaleza; CE; Brazil
2. Computer and Automation Research Institute; Hungarian Academy of Sciences; Budapest, P. O. Box 63; Budapest H-1518; Hungary
3. Projet Mascotte, I3S (CNRS UNSA) and INRIA 2004 Route des Lucioles; BP 93 06902; Sophia-Antipolis Cedex; France
4. CNRS, Laboratoire G-SCOP UMR 5272, Grenoble-INP; UJF-Grenoble 1; Grenoble F-38031; France