Univ. Orleans, INSA Centre Val de Loire, LIFO EA 4022, Orleans, France. marcilio.desouto@univ-orleans.fr.|Institute of Mathematics and Computer Sciences, University of São Paulo, São Carlos - SP, Brazil. pablo@icmc.usp.br.|Center of Informatics, Federal University of Pernambuco, Recife - PE, Brazil. ivan.costa@rwth-aachen.de.