Simple Object Access Protocol (SOAP) 1.1
The W3C Note on the Simple Object Access Protocol 1.1 submission.

SOAP: Simple Object Access Protocol Specification
The Internet Draft is the speficification of SOAP, which defines an RPC mechanism using XML for client/server interaction across a network by using HTTP as the base transport and XML documents for encoding of invocation requests and responses. By D. Box, G. Kakivaya, , A. Layman, S. Thatte, and D. Winer.

XML Protocol (XMLP) Requirements
Describes the XML Protocol Working Group's requirements for the XML Protocol (XMLP) specification.

SOAP Reference at Zvon
A complete reference which can be downloaded for off-line use.

Simple Object Access Protocol (SOAP) 1.2
W3C Working Draft 9 July 2001. SOAP version 1.2 is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol.

Asynchronous Web Services Protocol
Draft specification for an asynchronous web services protocol (AWSP).