Affiliation: | a Computer Science Department, University of Verona, Strada le Grazie, 15, 37134 Verona, Italy b DEIR, University of Sassari, via Torre Tonda, 34, 07100 Sassari, Italy c School of Computer Science, University of Manchester, Oxford Road, M13 9PL Manchester, UK d Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands |