[Standards] Business rules of Last Message Correction

Tedd Sterr teddsterr at outlook.com
Wed Jun 13 21:34:47 UTC 2018

> This wouldn’t be an issue if clients use sufficiently unique IDs.

I'm not sure that magically fixes the issue.
New RMC clients can and should use unique IDs - and we can mandate that - but the issue here is with older LMC non-RMC-aware clients.So, if those clients expect LMC to only ever be applied to the single recent message (possibly naive, but the XEP explicitly advises against doing older corrections without further negotiation) then upon discovering that the correction's ID does not match the most recent message, it can only assume that it never received the message that was to be corrected. This is true regardless of the uniqueness of the IDs (the ID of the last message and the correction don't match - which they shouldn't, because the correction is for an older message.)

> Also funny is by the way the question what counts as "Message" in this
> context. If I send a message and my client sends a CSN afterwards (because I
> switched to another tab maybe) and then I do a correction, is the CSN (which
> comes in its own <message/>) a new message, which should be prohibiting me
> from correcting my last actual text message?

One would hope (ha!) that implementations handle this in a sensible way; but it's probably worth being more explicit in specifying.

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