A man surfing on a green surfboard in a wave.
Nobody is surfing.
A man is different than nobody.
exists e1 s1 x1 x2 x3 x4.(a_topic(x1) & on(e1,x3) & in(x3,x4) & n_wave(x4) & n_surfboard(x3) & a_green(s1) & Theme(s1,x3) & Actor(e1,x2) & v_surf(e1) & (x1 = x2) & n_man(x1))
-exists e1 x1.(Actor(e1,x1) & v_surf(e1) & n_person(x1))