A dog swims in a pool.
the dog is a chihuahua
Not every dog is a chihuahua.
exists e1 x1 x2.(in(e1,x2) & n_pool(x2) & Actor(e1,x1) & v_swim(e1) & n_dog(x1))
exists p1 x1.(n_dog(x1) & exists x2.((x1 = x2) & n_chihuahua(x2)))