[1] Univ Alcala de Henares, Dept Comp Sci, E-28871 Alcala De Henares, Spain
[2] Slovak Univ Technol Bratislava, Fac Civil Engn, Dept Math & Descript Geometry, SK-81368 Bratislava, Slovakia
[3] Acad Sci Czech Republic, Inst Informat Theory & Automat, CZ-18208 Prague 8, Czech Republic