[1] Univ Warwick, Dept Comp Sci, Coventry CV4 7AL, W Midlands, England
[2] St Georges Univ London, Div Community Hlth Sci, London SW17 0RE, England
[3] Walailak Univ, Sch Informat, Tha Sala 80160, Nakhon Si Thamm, Thailand
[4] Univ Joensuu, Dept Comp Sci & Stat, FIN-80101 Joensuu, Finland