1. University of Patras, Greece
2. Computer Technology Institute & Press (CTI), Greece. E-mail: amaxilat@cti.gr
3. Department of Computer, Control, and Management Engineering (DIAG), Sapienza University of Rome, Italy. E-mails: ichatz@dis.uniroma1.it, vitaletti@dis.uniroma1.it
4. School of Applied Arts, Hellenic Open University, Greece. E-mail: mavrommati@eap.gr
5. Spark Works ITC Ltd, UK. E-mail: vasiliou.evi@sparkworks.net