Department of Information Technology, Faculty of Informatics, Masaryk University, 60200 Brno, Czech Republic. lexa@fi.muni.cz|Department of Information Technology, Faculty of Informatics, Masaryk University, 60200 Brno, Czech Republic. lexa@fi.muni.cz|Department of Information Technology, Faculty of Informatics, Masaryk University, 60200 Brno, Czech Republic. lexa@fi.muni.cz|Department of Information Technology, Faculty of Informatics, Masaryk University, 60200 Brno, Czech Republic. lexa@fi.muni.cz|Department of Information Technology, Faculty of Informatics, Masaryk University, 60200 Brno, Czech Republic. lexa@fi.muni.cz