As previously noted, I've been working to define interoperability between SIP and XMPP systems for many years, most recently in the STOX working group at the IETF. So we've published four different specifications covering various aspects of interworking, and today we've added a fifth: RFC 7702 on groupchat functionality. Big thanks to my co-authors: Saúl Ibarra Corretge and Salvatore Loreto! We're not quite done, though, because we still need to finish the document on signaling for managing multimedia sessions like audio and video calls. I'll be turning to that one next (well, that and fixes to the presence RFC).