HXP
SOAP specifications
The main goal of HXP is the development of a "common language"
in the form of standard procedure names compiled and published in a form of dictionary.
You can find the complete documentation of the SOAP protocol here:
http://www.w3.org/TR/soap12/ (Be warned: this is not as easy as the xml-rpc specs.
Compared to SOAP, xml-rpc specs sheet is like that 2-pages menu in your local restaurant)