C2MS11 — Revisit Tracking Fields

In C2MS 1.0, there is no indicator whether a tracking field (special fields in the Message Header and Heartbeat Messages) is required, optional or dependent. As such, in C2MS 1.1, we are marking these all optional, except for Heartbeat.SUBSCRIPTION.n.SUBJECT.PATTERN, which is being marked as dependent (required if NUM-OF-SUBSCRIPTIONS is > 0).

These should all be evaluated for R/O/D. One special case is HEARTBEAT.NUM-OF-SUBSCRIPTIONS. Normally, this should be required, because of C2MS11-135. However, in discussion for C2MS11-187, we went back to optional for this field. The rationale for this is that because it is a tracking field and therefore reserved for use by the PSM, rather than the generator of the message, it is difficult to understand what it means for a tracking field to be required. This reflects a shortcoming of the current C2MS documentation where it's not very clear what it means for a field to be a tracking field.

Finally, there are some tracking fields that should be considered for removal, such as CONNECTION-ID, MW-INFO, and USER from the Message Header. These fields seem useful for debugging, but not operations.

With the context stated above, the following need to be addressed in a future revision of C2MS:

• Revisit which tracking fields should remain and deprecate the others.
  • • As part of this, note that outside the Message Header, the only C2MS message that defines tracking fields is the Heartbeat Message. Do these belong? It just seems strange.
• Determine R/O/D (required/optional/dependent) for each tracking field. Note that in an OMG meeting in Jan, 2024, broad-brushing it, it appeared that UNIQUE-ID and PUBLISH-TIME in the Message Header and NUM-OF-SUBSCRIPTIONS in the Heartbeat could be required, and the others optional in the Message Header.
• Document the expected use for these tracking fields, including:
  • • What the expected population of tracking fields is by both the Message Sender and the underlying PSM. (example, many of these are set as part of the GMSEC API and are supposed to be left alone before invoking the API in the one PSM that we currently have, but this is inner-workings knowledge and not clearly specified in C2MS).
    • What the expected use of these tracking fields, if any, is by a Message Recipient. For example, are these stripped off by the PSM before delivery? That would be symmetrical if the PSM populates the fields, but no mention of this exists in the current documentation. Some fields may be handled differently from others... for example UNIQUE-ID makes sense, but is the PSM really going to deliver CONNECTION-ID to the Message Recipient?
    • What does it mean if a tracking field is required? If only the PSM sets them, this would mean that a message would have to be created without a required field and then handed to the PSM, which is required to populate it.... this all needs clarity in the documentation.