Programming Web Services with SOAP

Chapter 2. Introducing SOAP

SOAP's place in the web services technology stack is as a standardized packaging protocol for the messages shared by applications. The specification defines nothing more than a simple XML-based envelope for the information being transferred, and a set of rules for translating application and platform-specific data types into XML representations. SOAP's design makes it suitable for a wide variety of application messaging and integration patterns. This, for the most part, contributes to its growing popularity.

This chapter explains the parts of the SOAP standard. It covers the message format, the exception-reporting mechanism (faults), and the system for encoding values in XML. It discusses using SOAP over transports that aren't HTTP, and concludes with thoughts on the future of SOAP. You'll learn what SOAP does and how it does it, and get a firm understanding of the flexibility of SOAP. Later chapters build on this to show how to program with SOAP using toolkits that abstract details of the XML.

SOAP and XML

SOAP is XML. That is, SOAP is an application of the XML specification. It relies heavily on XML standards like XML Schema and XML Namespaces for its definition and function. If you are not familiar with any of these, you'll probably want to get up to speed before continuing with the information in this chapter (you can find information about each of these specifications at the World Wide Web Consortium's web site at http://www.w3c.org). This book ...