A dog swims in a pool.
A dog dives into a pool after his toy.
The dog may not be swimming after his toy.  Not all dogs are boys.  The dog did not necessarily dives into the pool.
exists e1 x1 x2.(in(e1,x2) & n_pool(x2) & Actor(e1,x1) & v_swim(e1) & n_dog(x1))
exists e1 x1 x2 x3.(after(e1,x3) & n_toy(x3) & of(x3,x1) & n_male(x1) & into(e1,x2) & n_pool(x2) & Actor(e1,x1) & v_dive(e1) & n_dog(x1))