A dog looking over the backs of sheep.
a border collie herding some sheep
Not all dogs are a border collie.  Although the dog is looking over the sheep, it does not imply the dog is herding the sheep.
exists e1 x1 x2 x3 x4.(n_back(x3) & a_topic(x1) & over(e1,x3) & of(x3,x4) & n_sheep(x4) & Actor(e1,x2) & v_look(e1) & (x1 = x2) & n_dog(x1))
exists e1 x1 x2 x3 x4.(a_topic(x1) & Theme(e1,x4) & Actor(e1,x3) & v_herd(e1) & n_sheep(x4) & (x1 = x3) & n_collie(x1) & of(x1,x2) & n_border(x2))