The protocol documented by this schema is defined in XEP-0009: http://www.xmpp.org/extensions/xep-0009.html There is no official XML schema for XML-RPC. The main body of this schema has been borrowed from an unofficial schema representation contained in the book "Processing XML With Java" by Elliotte Rusty Harold, as located at: http://www.ibiblio.org/xml/books/xmljava/chapters/ch02s05.html