1. GSyA and ISTR Research Groups, Dep. of Computer Science and Electronics, Faculty of Sciences, Univeristy of Cantabria, Santander, Spain
2. Alarcos Research Group. Institute of Information Technologies and Systems, Dep. of Information Technologies and Systems, Escuela Superior de Informática, Univ. of Castilla-La Mancha, Ciudad Real, Spain
3. GSyA Research Group. Institute of Information Technologies and Systems, Dep. of Information Technologies and Systems, Escuela Superior de Informática, University of Castilla-La Mancha, Ciudad Real, Spain
4. Lucentia Research Group. Dep. of Information Languages and Systems, Facultad de Informática, University of Alicante, Alicante, Spain