A guy on a snowboard grinding.
A guy is preparing to start snowboarding.
If the snowboarder is grinding, he or she is not preparing to start snowboarding but is already doing so.
exists e1 x1 x2 x3.(a_topic(x1) & on(x1,x2) & Actor(e1,x3) & v_grind(e1) & (x2 = x3) & n_snowboard(x2) & n_guy(x1))
exists e1 p1 x1.(Topic(e1,p1) & Actor(e1,x1) & v_prepare(e1) & exists e2 p2.(exists e3.(Actor(e3,x1) & v_snowboard(e3)) & Topic(e2,p2) & Actor(e2,x1) & v_start(e2)) & n_guy(x1))