The SOAP Version 1.2 specifications from the W3C XML Protocol Working Group define the required core of SOAP 1.2 (Part 1 of the specification), and a number of optional parts such as a graph encoding, a convention for RPC, and an HTTP binding (Part 2). There is also a primer (Part 0) and a test collection document. These specifications are expected to become a W3C Recommendation in June 2003.

One of the success factors for web services has been the emergence of XML as the neutral lingua franca of machine to machine interaction. SOAP complements XML in this role by providing the unit of messaging - the SOAP envelope - for web services. The Messaging Framework, Part 1 of the SOAP

1.2 specification, describes the envelope along with a detailed model for its processing, plus mechanisms for extension, handling of messages by intermediaries, and error generation. And it is within this framework description that the major differences between the 1.1 and 1.2 versions of SOAP occur.

Part 2 of the specification, "Adjuncts", defines additional parts that are optional although they are included because they are likely to be generally useful. For example, the HTTP binding which is described using SOAP 1.2's new extensibility model is expected to be widely implemented. It has been updated in SOAP 1.2 to bring it more in line with the architecture of the Web, providing an HTTP GET method to request SOAP responses. Another adjunct describes a convention for Remote Procedure Calls that are carried within SOAP envelopes. SOAP has been considered as simply a mechanism for RPCs over HTTP, however the optionality of both HTTP and RPC in the new specification signals a wider role for SOAP 1.2.

SOAP 1.2 was validated by gathering implementation evidence to show that the different features of the specification were indeed implementable. These features, and examples of SOAP messages that test them, form the basis of the test collection part of the specification.

As the Working Group's work on the main SOAP 1.2 specification has neared completion, it has started work on a new extension. Specifically, it has started work on a mechanism for serializing large chunks of data (typically in a binary format) without having to incur the overhead of using base64 encoding. During the session, we will report on this "attachments" work, along with any other errata or updates to the main specification.