A girl in a helmet rides a horse.
The child is a competitive horseback rider.
Not all people riding horses ride in a competitive way.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_ride(e1) & n_horse(x3) & in(x1,x2) & n_helmet(x2) & n_girl(x1))
exists p1 x1.(n_child(x1) & exists s1 x2 x3.((x1 = x2) & n_rider(x2) & of(x2,x3) & n_horseback(x3) & a_competitive(s1) & Theme(s1,x2)))