Department of Computer and Information Science, Linköpings Universitet, Sweden. lestr@ida.liu.se|Department of Computer and Information Science, Linköpings Universitet, Sweden. lestr@ida.liu.se|Department of Computer and Information Science, Linköpings Universitet, Sweden. lestr@ida.liu.se|Department of Computer and Information Science, Linköpings Universitet, Sweden. lestr@ida.liu.se