DDS11 — (R#133) Clarify meaning of LivelinessLost and DeadlineMissed

The specification does not state whether the LivelinessLostStatus should be considered changed (and the on_liveliness_lost listener callback called) once-when the writer first lost its liveliness-or whether should it be called after every period in which the writer fails to assert its liveliness. For example, if a writer with liveliness set to MANUAL_BY_TOPIC doesn't write for two LIVELINESS lease_duration periods, should the writer listener's on_liveliness_lost callback be called once per lease_duration, or should the callback be called only once after the first lease_duration?

The analogous ambiguity exists with respect to the *DeadlineMissedStatuses.

Proposed Resolution:

The cases are somewhat different in that the deadline is under the application's control while a loss of liveliness is not (e.g. it may occur as a result of a network failure). Therefore, the *DeadlineMissed statuses should be considered changed (and the listeners invoked) at the end of every deadline period. The LivelinessLostStatus, on the other hand, should be considered changed only when a writer's state changes from alive to not alive, not after every lease_duration period thereafter.

Proposed Revised Text:

Change the description in the RequestedDeadlineMissed total_count row of the table in 2.1.4.1 (page 2-118) to read: "Total cumulative number of missed deadlines detected for any instance read by the DataReader. Missed deadlines accumulate; that is, each deadline period the total_count will be incremented by one for each instance for which data was not received."

Change the description in the LivelinessLostStatus total_count row of the table in 2.1.4.1 (page 2-119) to read: "Total cumulative number of times that a previously-alive DataWriter became not alive due to a failure to actively signal its liveliness within its offered liveliness period. This count does not change when an already not alive DataWriter simply remains not alive for another liveliness period."

Change the description in the OfferedDeadlineMissed total_count row of the table in 2.1.4.1 (page 2-119) to read: "Total cumulative number of offered deadline periods elapsed during which a DataWriter failed to provide data. Missed deadlines accumulate; that is, each deadline period the total_count will be incremented by one."

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