Persistent XMPP MUC (XEP-45), like WhatsApp groupchats

Question

From the spec —

7.14 Exiting a Room

In order to exit a multi-user chat room, an occupant sends a presence stanza of type \"unavailable\"

Answer 1

XEP-45 was designed more then 10 years ago. Back then, the designers had something like IRC channels in mind. Everything of XEP-45 is designed based on the assumption that a user enters and leaves a room when he/she starts/terminates its client.

WhatsApp Groupchats are different: A user joins a groupchat is is able to view the (complete) history of that chat. Even if the users client is offline/unavailable, he is still considered part of the groupchat.

The XMPP community currently works on a new XEP that provides such functionality. It is called XEP-0369: Mediated Information eXchange. It is the spiritual successor of XEP-0045, providing the features one would expect from modern groupchats.