In the first place, I would like to thank, above all, my advisor Prof. Marco Antonio Casanova for his boundless patience, for helping me find a topic that was both challenging and suitable for a master's degree and also for having guided me in the steps towards the publication of an article.Further, I would like to thank PUC-Rio and CAPES for providing a tuition scholarship. It was an honor to be part of the "Programa de Pós-graduação emInformática". This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -Brasil (CAPES) -Finance Code 001.To Michael Kelly, my friend and English guru, for helping me with the language.For my colleagues at Grupo Santa Isabel, especially Creston Fernandes, Isabel Ferraz Magalhães and Ferdinando Valle Magalhães for understanding the importance of this project for me and allowing me to dedicate the needed the time to complete it.