a horse and rider jump over a fence.
A horse racing.
not every horse that jumps a fence is racing
exists s1 x1 x2 x3 x4.(a_topic(s1) & subset_of(x2,s1) & over(x2,x4) & n_fence(x4) & n_jump(x2) & of(x2,x3) & n_rider(x3) & subset_of(x1,s1) & n_horse(x1))
exists x1 x2.(a_topic(x1) & n_racing(x1) & of(x1,x2) & n_horse(x2))