The Baseline Specifications of Web Service Architecture
The baseline specifications are the standards on which the Web service architecture builds to provide many of the other features needed in many distributed applications. The protocols that form the basis of the Web service architecture include SOAP, WSDL, and UDDI.
You can think of XML and HTTP as pre-baselines. But SOAP, UDDI, and WSDL are really where the Web services world begins in earnest. Chapter 2 (XML Web Services Standards) details how these standards are linked together, and how they provide a simple, modular architecture for building, describing, and finding Web services.