A man stands on the back of a trash truck.
A man is smoking on the back of a truck
The man stands on the back of a trash truck but that doesn't mean that he is smoking.
exists e1 x1 x2 x3 x4.(n_back(x2) & on(e1,x2) & of(x2,x3) & n_truck(x3) & of(x3,x4) & n_trash(x4) & Actor(e1,x1) & v_stand(e1) & n_man(x1))
exists e1 x1 x2 x3.(n_back(x2) & on(e1,x2) & of(x2,x3) & n_truck(x3) & Actor(e1,x1) & v_smoke(e1) & n_man(x1))