1. Department of Information Science and Media Studies, University of Bergen, Bergen, Norway. E-mail: Andreas.Opdahl@uib.no
2. LabSTICC, University of South Brittany, Lorient, France. E-mail: Giuseppe.Berio@univ-ubs.fr
3. LINA, University of Nantes, Nantes, France. E-mail: Mounira.Harzallah@univ-nantes.fr
4. Institute of Computer Science, University of Tartu, Tartu, Estonia. E-mail: rma@ut.ee