Department of informatics, University of Bergen, PB. 7800, N-5020 Bergen, Norway. haraldb@ii.uib.no|Department of informatics, University of Bergen, PB. 7800, N-5020 Bergen, Norway. haraldb@ii.uib.no|Department of informatics, University of Bergen, PB. 7800, N-5020 Bergen, Norway. haraldb@ii.uib.no