1. INESC TEC, University of Trás-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal
2. College of Information Science & Technology, University of Nebraska at Omaha, Omaha, NE 68182, USA
3. Postgraduate Program in Informatics, PPGI/UFRJ, Rio de Janeiro 21941-916, Brazil
4. Tércio Pacitti Institute of Computer Applications and Research (NCE), Federal University of Rio de Janeiro, Rio de Janeiro 21941-916, Brazil
5. Systems Engineering and Computer Science Program (PESC/COPPE/UFRJ), Rio de Janeiro 21941-972, Brazil