1. Department of Information; Electric Engineering and Applied Mathematics; University of Salerno; Fisciano SA 84084 Italy
2. School of Computer Science and Informatics; Faculty of Technology; De Montfort University; Leicester LE1 9BH UK
3. Department of Computer Science and Artificial Intelligence; University of Granada; Granada 18071 Spain
4. Faculty of Software and Information Science; Iwate Prefectural University; Iwate Japan
5. Department of Management and Innovation Systems; University of Salerno; Fisciano SA 84084 Italy