Hi, Just in case no-one had happened to consider, there's the W3C's spec "Remote Events for XML" (http://www.w3.org/TR/rex/) which could (or not) be used in xep 228, Shared Editing. Some parts of it seemed a little verbose to me at first, but on another look it felt ok... however, I wouldn't wonder if it was checked out and scrapped already.
-janne
