Department of Information Technology, University of Turku, Turku, Finland. jari.bjorne@utu.fi|Department of Information Technology, University of Turku, Turku, Finland. jari.bjorne@utu.fi|Department of Information Technology, University of Turku, Turku, Finland. jari.bjorne@utu.fi|Department of Information Technology, University of Turku, Turku, Finland. jari.bjorne@utu.fi|Department of Information Technology, University of Turku, Turku, Finland. jari.bjorne@utu.fi