A group of spectators watch a man ride a bull.
A man is ride a bull while no one is watching.
A man riding a bull can either have a group of spectators watching, or he can be riding while no one is watching. There can either be a group or no one, but not both.
exists x1 x2.(all x3.(n_bull(x3) -> exists e1 x4 x5.(Theme(e1,x4) & Actor(e1,x1) & v_watch(e1) & for(x4,x3) & n_ride(x4) & of(x4,x5) & n_man(x5))) & of(x1,x2) & n_spectator(x2) & n_group(x1))
exists e1 p1 x1 x2.(-exists e2 x3.(Actor(e2,x3) & v_watch(e2) & n_one(x3)) & while(e1,p1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_bull(x2) & n_man(x1))