1. Department of Computer, Control and Management Engineering “Antonio Ruberti”, Sapienza University of Rome, Via Ariosto 25, 00185 Rome, Italy. E-mails: valentina.franzoni@dmi.unipg.it, daniele.nardi@uniroma1.it
2. Department of Mathematics and Computer Science, University of Perugia, Via Vanvitelli 1, 06123 Perugia, Italy. E-mail: milani@unipg.it
3. Philosophy Department, Universitat Autònoma de Barcelona, 08193, Bellaterra (BCN), Catalonia, Spain. E-mail: jordi.vallverdu@uab.cat