1. Department of Computer Science, Multimedia and Telecommunication, Universitat Oberta de Catalunya, 08018 Barcelona, Spain
2. Spindox España S.L., Calle Muntaner 305, 08021 Barcelona, Spain
3. Research Center on Production Management and Engineering, Universitat Politècnica de València, Plaza Ferrandiz-Salvador, 03801 Alcoy, Spain
4. Department of Telecommunications & Systems Engineering, Universitat Autònoma de Barcelona, 08202 Sabadell, Spain
5. Department of Computer Architecture & Operating Systems, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain