Re: A Design Problem

S Perryman <q@xxxxx> wrote:
Daniel T. wrote:

With a synchronous message the postcondition is *at most*
"delivered", "understood", or "processed"

Wrong. The post-condition is *at the very least* ... (which is what
Dmitry stated when he wrote "the postcondition also includes" ) .

I miss-spoke. I am advocating that the most flexible systems have
methods with such postconditions. Yes, a client can require much more
from a server (the client can make the specification so stringent that
it can only be satisfied by a single algorithm,) but that limits what
the server is allowed to do in response.

To borrow from Meyer, "The postcondition True is the weakest possible
assertion, satisfied by all states." With such a postcondition, the
message receiver will do the right thing regardless of what it does (as
long as the receiver passes control back to the sender in a finite
amount of time.) That gives the receiver maximum flexibility in
implementation, and since an OO program is full of message receivers,
the more of them that have this flexibility, the more flexible the
program is over all.
.