Paolo Bottoni Maria De Marsico Paolo Di Tommaso Stefano Levialdi Domenico Ventriglia Definition of visual processes in a language for expressing transitions. 211-242 2004 15 J. Vis. Lang. Comput. 3-4 http://dx.doi.org/10.1016/j.jvlc.2004.01.002 db/journals/vlc/vlc15.html#BottoniMTLV04