Proposed resolution for Rel 50

[Jacques Durand <JDurand@fsw.fujitsu.com>]

Title: Proposed resolution for Rel 50

Rel 50: Semantics of ExpiryTime:
-------------------------------

Proposal:

ExpiryTime indicates the ultimate date after which the receiver RMP will
not accept a message. In order to be accepted by an RMP, a message
must have schema-valid RM headers, and must not have expired.
Only accepted messages are subject to further processing by the RMP.

When receiving a message after its ExpiryTime date, an RMP MUST NOT accept the message.
Once a message has been accepted by the RMP, the fact that the message expires while
being processed by the RMP MUST NOT affect its processing, nor its final availability
status to the receiver application. Such expired messages must still be delivered to
the application, assuming they satisfy other reliability requirements.

NOTE:
Although ExpiryTime will not affect further the processing of accepted messages,
it is useful for an RMP to remember it in order to avoid unnecessary duplicate checks
with future messages, when "at most once" delivery is required.
Given the above definition of ExpiryTime, it is impossible that a received message M
accepted by the RMP, is a duplicate of past messages that are expired at the time M
was accepted.