1. Department of Informatics and Telecommunications, University of Peloponnese, Tripolis, Greece. ckoutras@uop.gr
2. KR Group, Department of Computer Science, University of Liverpool, Liverpool, UK. C.Moyzes@liverpool.ac.uk
3. Institut de Recherche en Informatique de Toulouse (IRIT), Toulouse, France. Christos.Rantsoudis@irit.fr