I’ve been interested in Instant Messaging and Presence for some time now. A number of protocol groups were spawned from the IMPP effort including XMPP, an XML based protocol that is the core for the Jabber project.
Now, separately, an array of specifications have been written for web services, which are fundamentally about exchanging messages with support for security, reliability, addressing, routing, and subscriptions amongst other things; in fact, most of the things in the requirements document for IMPP RFC 2779. Once all the tools support for these specifications appears, it would be interesting to see how little code would need to be written to construct an interoperable IM protocol. In the meantime, Bruce Williams has a blog post describing the WS-Eventing specification.