1. Ph.D. Researcher, Dept. of Computer Science and Artificial Intelligence, Univ. of Granada, CL Daniel Saucedo Aranda s/n, 18071 Granada, Spain; Consejo Superior de Investigaciones Científicas (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain (corresponding author).
2. Professor, Dept. of Computer Science and Artificial Intelligence, Univ. of Granada, CL Daniel Saucedo Aranda s/n, 18071 Granada, Spain.