(1) Department of Computer Science, University of Bari Aldo Moro, Italy
(2) School IV - Electrical Engineering and Computer Science, Berlin Institute of Technology, Germany
(3) Electrical & Electronics Engineering Department, Technical University of Bari, Italy
(4) Italian National Research Council (ISTC-CNR), Institute for Cognitive Sciences and Technology, Italy
(5) National University of Ireland (NUIG), Galway. DERI - Digital Enterprise Research Institute, Ireland
(6) Department of Computer Science, University of Oxford, United Kingdom