A surfer is riding a wave.
The person is on a wave on a surf board.
Not all surfer riding a wave on a surf board.
exists e1 x1 x2.(Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_wave(x2) & n_surfer(x1))
exists p1 x1.(n_person(x1) & exists s1 x2 x3.(on(x1,x2) & on(x2,x3) & n_board(x3) & a_surf(s1) & Theme(s1,x3) & n_wave(x2)))