bull rider on the ground
The person was riding a horse.
A bull rider rides a bull and not a horse
exists x1 x2 x3.(n_ground(x3) & a_topic(x1) & on(x1,x3) & n_rider(x1) & of(x1,x2) & n_bull(x2))
exists e1 x1 x2.(n_person(x1) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_horse(x2))