XP - Extensible Protocol
IETF - http//www.ietf.org/internet-drafts/draft-harding-extensible-protocol-00.txt
Sets up two streams passing information as request/response
Java implementation available
“To extend XML from a class of data objects into a protocol is to extend the rules for constructing a single document into rules for constructing two interrelated streams of documents. Accordingly, we introduce mechanisms for handling both the sequential and interrelated aspects of the document streams.”