The W3C XML Protocol Working Group has released a revised working draft document for the XML Protocol (XMLP) Requirements. This WD updates the previous version of 2000-12-19, and "describes the W3C XML Protocol Working Group's requirements for the XML Protocol (XMLP) specification." XMLP "allows two or more peers to communicate in a distributed environment using XML as its encapsulation language. The XMLP framework can accommodate an open-ended set of XMLP modules defining a large variety of functions and services. Typical functions and services defined by XMLP modules can range from generic mechanisms for handling security, caching, routing, and eventing to specific functions like submitting a purchase order. While XMLP itself is intended to be as simple and lightweight as possible, XMLP modules can be designed and composed to perform arbitrarily complex operations allowing the core protocol to remain simple." The working draft articulates external requirements from XForms and P3P in addition to the general requirements and related requirements areas (simplicity and stability; data encapsulation and evolvability; intermediaries; data representation; protocol bindings; convention for RPC). A Glossary in the document overviews the general protocol concepts, data encapsulation concepts, message sender and receiver concepts, and data representation concepts. The draft also specifies usage scenarios, intended to provide representative examples of situations where XMLP might be applicable.

Bibliographic information: XML Protocol (XMLP) Requirements. Reference: W3C Working Draft 19-March-2001. Edited by Vidur Apparao (Netscape), Alex Ceponkus (Bowstreet), Paul Cotton (Microsoft), David Ezell (Hewlett Packard), David Fallside (IBM(, et al.. Latest version URL: http://www.w3.org/TR/xmlp-reqs/. This draft updates the previous version of 2000-12-19.

From the WG charter:

The XML Protocol Working Group is chartered to design the following four components:

• An envelope for encapsulating XML data to be transferred in an interoperable manner that allows for distributed extensibility and evolvability as well as intermediaries.
• A convention for the content of the envelope when used for RPC (Remote Procedure Call) applications. The protocol aspects of this should be coordinated closely with the IETF and make an effort to leverage any work they are doing.
• A mechanism for serializing data representing non-syntactic data models such as object graphs and directed labeled graphs, based on the datatypes of XML Schema.
• A mechanism for using HTTP transport in the context of an XML Protocol. This does not mean that HTTP is the only transport mechanism that can be used for the technologies developed, nor that support for HTTP transport is mandatory. This component merely addresses the fact that HTTP transport is expected to be widely used, and so should be addressed by this Working Group.