Department of Computer Science, University of Warwick, Coventry, United Kingdom. Dimitris.Vavoulis@dcs.warwick.ac.uk|Department of Computer Science, University of Warwick, Coventry, United Kingdom. Dimitris.Vavoulis@dcs.warwick.ac.uk|Department of Computer Science, University of Warwick, Coventry, United Kingdom. Dimitris.Vavoulis@dcs.warwick.ac.uk|Department of Computer Science, University of Warwick, Coventry, United Kingdom. Dimitris.Vavoulis@dcs.warwick.ac.uk