A jockey riding a brown horse.
A jockey is riding his horse in a race
A jockey rides many horses, they do not necessarily belong to him.  Also, just because a jockey is riding a horse does not mean they are currently entered in a race.
exists e1 s1 x1 x2 x3.(a_topic(x1) & Theme(e1,x3) & Actor(e1,x2) & v_ride(e1) & n_horse(x3) & a_brown(s1) & Theme(s1,x3) & (x1 = x2) & n_jockey(x1))
exists e1 x1 x2 x3.(in(e1,x3) & n_race(x3) & Theme(e1,x2) & Actor(e1,x1) & v_ride(e1) & n_horse(x2) & of(x2,x1) & n_male(x1) & n_jockey(x1))