A guy is doing a trick on a bike.
Boy in a bike competition
You can not infer he is in competition.
exists e1 x1 x2 x3.(Theme(e1,x2) & Actor(e1,x1) & v_do(e1) & on(x2,x3) & n_bike(x3) & n_trick(x2) & n_guy(x1))
exists s1 x1 x2.(ne_nam_boy(s1) & a_topic(s1) & in(s1,x1) & n_competition(x1) & of(x1,x2) & n_bike(x2))