Children playing on rocks.
The children are playing video games.
The children cannot be playing video games and on rocks at same time.
exists e1 x1 x2 x3.(a_topic(x1) & on(e1,x3) & n_rock(x3) & Actor(e1,x2) & v_play(e1) & (x1 = x2) & n_child(x1))
exists e1 x1 x2 x3.(n_child(x1) & Theme(e1,x2) & Actor(e1,x1) & v_play(e1) & n_game(x2) & of(x2,x3) & n_video(x3))