Re: A Design Problem

"Dmitry A. Kazakov" <mailbox@xxxxxxxxxxxxxxxxx> wrote:
On Sat, 25 Aug 2007 22:41:55 -0400, Daniel T. wrote:

To get back to a programming example. A Subject sends a message to its
Observers when its state changes. Does the Subject do this to cause an
effect? Of course not.

Of course yes. It does this in order to have the message sent. The message
is an object and the messages propagation substrate is an object too. The
postcondition of sending an asynchronous message is at least "the message
is underway." In a more carefully designed system messages have meanings
and the meaning is also a part of the postcondition. Then for synchronous
messages the postcondition also includes "delivered", "understood",
"processed", "replied."

FInally! I can agree with everything you say above, with only a slight
edit.

The postcondition of sending an asynchronous message is *at most* "the
message is underway". With a synchronous message the postcondition is
*at most* "delivered", "understood", or "processed". Designing a system
in this way allows for maximum flexibility.
.