A boy on a BMX bike
The BMX rider is performing in a competition.
The boy may not be performing in a competition or even riding the bike.
exists x1 x2 x3.(a_topic(x1) & on(x1,x2) & n_bike(x2) & (x2 = x3) & ne_org_bmx(x3) & n_boy(x1))
exists e1 x1 x2 x3.(n_rider(x1) & (x1 = x2) & ne_org_bmx(x2) & in(e1,x3) & n_competition(x3) & Actor(e1,x1) & v_perform(e1))