bull rider on the ground
The person is on the ground.
A bull rider is a person, and the ground is the ground.
exists x1 x2 x3.(n_ground(x3) & a_topic(x1) & on(x1,x3) & n_rider(x1) & of(x1,x2) & n_bull(x2))
exists p1 x1 x2.(n_ground(x2) & n_person(x1) & on(x1,x2))