A boy standing on railing
Some is standing on railing.
A boy standing on railing is not the same a some.
exists e2 e1 x1 x2 x3.(a_topic(x1) & on(e1,e2) & Actor(e2,x3) & v_rail(e2) & Actor(e1,x2) & v_stand(e1) & (x1 = x2) & n_boy(x1))
exists e1 x1 x2.(on(e1,x2) & n_railing(x2) & Actor(e1,x1) & v_stand(e1) & n_thing(x1))