I've done some implementation of the XEP and have done some basic interoperability testing with other implementers. I ran into some issues due to the fact where it is not clear which stanzas are required and which are optional. For example, is the <id> stanza element required in the <entry> and <source> stanzas? I would think they would be in order to support threaded conversations since the <id> is used in the in-reply-to element.
However would it be possible for the XEP to be amended to include a XML schema, and also a note on which elements are required for a minimum implementation? Thanks
