The Danger of Weak Post-conditions:
The weakest possible post-condition is:
Q = True is always satisfied (will never be False).
A’s behavior is arbitrary (as long as it terminates).
P = ? is a don’t-care pre-condition.
(Why does Meyer say that this is only the second-best job in the world?)
A nontrivial A must satisfy stronger post-conditions (to specify all the services required by its clients) .