A surfer on a roiling wave.
An expert surfer surfing
Surfers on a roiling wave may have competence less than that of an expert.
exists e1 x1 x2.(a_topic(x1) & on(x1,x2) & n_wave(x2) & Actor(e1,x2) & v_roil(e1) & n_surfer(x1))
exists x1 x2 x3.(a_topic(x1) & n_surfing(x1) & of(x1,x3) & n_surfer(x3) & of(x1,x2) & n_expert(x2))