A boy surfs on a wave.
A person in the water.
A boy is a person. Surfing is done in the water.
exists e1 x1 x2.(on(e1,x2) & n_wave(x2) & Actor(e1,x1) & v_surf(e1) & n_boy(x1))
exists x1 x2.(n_water(x2) & a_topic(x1) & in(x1,x2) & n_person(x1))