Chapter 8. SOAP

SOAP is a simple, extensible XML protocol framework for communication between distributed peer processes [SOAP]. It does not define specific application semantics. This book includes a discussion of SOAP for the following reasons:

• Chapter 11 uses SOAP as an example of the application profiling of XMLDSIG authentication.

• The XML key management protocol (XKMS), as described in Chapter 14, commonly uses SOAP.

• Some problems related to exclusive versus inclusive canonicalization were first actually encountered in connection with SOAP use. SOAP illustrates these problems, as described in Chapter 9.

• SOAP is an example of a protocol use of XML (see Appendix E).

An understanding of SOAP is not necessary to achieve a general understanding of XML digital signatures (Chapter 10) or XML encryption (Chapter 15). If you are already familiar with SOAP, you can skip this chapter.

Section 8.1 introduces SOAP. Next, Section 8.2 specifies the basic structure of SOAP messages, explains how they are exchanged and processed, and considers error handling under SOAP. Section 8.3 describes the syntax for encoding information being sent with this protocol as well as a method for indicating other encoding syntaxes. In Section 8.4, the binding of SOAP to particular transport protocols, including HTTP, is considered [RFC 2616]. Finally, Section 8.5 describes a method of performing remote procedure calls through SOAP.