These assumptions seem reasonable for XMPP MUC:
- All members see the same message order (assigned by server)
- All messages are broadcast to group
We probably need another assumption regarding reliability and disconnection. Maybe something like:
"A client can detect when it's in a situation where message delivery might be unreliable (e.g. due to TCP connection close, or heartbeat failure)"
In this case the client could re-join the group, so we can distinguish client-server connection problems from other transcript consistency problems.