Two people go dirt bike racing.
The BMX riders compete on the dirt track.
Dirt bike does not imply BMX
exists e1 x1 x2 x3 x4.(Theme(e1,x2) & Actor(e1,x1) & v_go(e1) & n_racing(x2) & of(x2,x4) & n_bike(x4) & of(x2,x3) & n_dirt(x3) & n_people(x1) & card_eq_2(x1))
exists e1 x1 x2 x3 x4.(n_track(x3) & of(x3,x4) & n_dirt(x4) & n_rider(x1) & (x1 = x2) & ne_org_bmx(x2) & on(e1,x3) & Actor(e1,x1) & v_compete(e1))