Another notify question

Recently I inquired about the notify command, and I was very pleased with the
response I recieved. I am glad the developers have decided to implement a
string argument in the future.

The discussion about implementation has lead me to the following question:
What should I be sure that notify will do? Tom seems to think that delivery
of a notification should not be guarenteed (if I understand what he is
saying), which is fine with me. However, I would like to know what the
specification of notify is so that I can adjust my application accordingly.
If I might not recieve a notification, or if I might recieve too many, I
would like to know.

Regards,
    Jeff