Institute for Computing Applications M. Picone, National Research Council (CNR), V.le del Policlinico, 13700161 Rome, Italy.|Institute for Computing Applications M. Picone, National Research Council (CNR), V.le del Policlinico, 13700161 Rome, Italy.|Institute for Computing Applications M. Picone, National Research Council (CNR), V.le del Policlinico, 13700161 Rome, Italy.