A person stands on a mountaintop.
person standing
A person on a moutaintop doesn't imply the person is standing
exists e1 x1 x2.(on(e1,x2) & n_mountaintop(x2) & Actor(e1,x1) & v_stand(e1) & n_person(x1))
exists e1 x1 x2.(a_topic(x1) & Actor(e1,x2) & v_standing(e1) & (x1 = x2) & n_person(x1))