1. Department of Computer Engineering, Universidad de Alcalá, Alcalá de Henares, Spain
2. Department of Computer Science, University of Freiburg, Freiburg, Germany
3. Interdisciplinary Graduate School, Nanyang Technological University, Jurong West, Singapore
4. Dipartimento di Informatica, Sistemistica e Comunicazione, Università degli Studi di Milano - Bicocca, Milan, Italy