SOAP is Posted as a Note to W3C

On, 8 May 2000, Simple Object Access Protocol (SOAP) 1.1 was posted as at Note to the W3C.  This document was submitted to the W3C  to propose the formation of a working group in the area of XML-based protocols. At this point in time, W3C has had no editorial control over the preparation of SOAP 1.1. It is a work in progress and may be updated, replaced, or rendered obsolete by other documents at any time.

The authors of SOAP include Don Box, DevelopMentor, David Ehnebuske, IBM, Gopal Kakivaya, Microsoft, Andrew Layman, Microsoft, Noah Mendelsohn, Lotus Development Corp., Henrik Frystyk Nielsen, Microsoft, Satish Thatte, Microsoft, and Dave Winer, UserLand Software, Inc.  While many of the participants are from Microsoft, it is interesting to note the participation by the usual Microsoft rival, IBM/Lotus.

SOAP provides a lightweight XML-based protocol for exchange of information in a decentralized, distributed environment. The SOAP protocol consists of three parts: the "SOAP envelope" that defines a framework for describing what is in a message and how to process it, a set of "SOAP encoding rules" for expressing instances of application-defined datatypes, and a convention for representing remote procedure calls and responses called "SOAP RPC. "

Although these parts are described together as SOAP, they are functionally orthogonal. In particular, the envelope and the encoding rules are defined in different namespaces in order to promote simplicity through modularity.  In addition to the SOAP envelope, the SOAP encoding rules and the SOAP RPC conventions, this specification defines two protocol bindings that describe how a SOAP message can be carried in HTTP either with or without the HTTP Extension Framework.  SOAP messages are fundamentally one-way transmissions from a sender to a receiver.  SOAP messages can be combined to implement patterns such as request/response.

SOAP enables applications to communicate with each other in a rich way over the Web's infrastructure. Today, the bulk of Web traffic consists of browsers connecting to servers and retrieving HTML pages for the human user to view. SOAP extends the capability of the Web by enabling applications to communicate with other applications, and it provides a framework for connecting Web sites and applications to create Web services.

SOAP provides an underlying mechanism for each Web service to expose its features and communicate with other services. Imagine an application that links together directions you get from an online mapping site with real-time traffic data from a Department of Transportation site and with information about when you're supposed to be at your destination retrieved from your calendar. The result could be an application that reminds you to leave 15 minutes early to get to your destination, and re-routes you around a traffic accident.  With SOAP, you can link these services together as components and build this kind of application very quickly. SOAP enables homogenous or heterogeneous components to communicate over the Internet as well as coarse-grained, service-to-service communication and component-to-service communication.

Today, you might invoke remote objects using some kind of binary protocol such as DCOM, RMI, or CORBA IIOP. This means that client applications are designed to communicate with specific server applications. It also means that if you want to run applications that are outside your firewall, you need to "punch holes" in your firewall in order for a client and server to talk to each other. SOAP fixes both of these problems by enabling applications to more easily discover each other's capabilities and to run seamlessly over the Web.  SOAP provides a way to use the Web infrastructure to enable applications to communicate directly with each other without being unintentionally blocked by firewalls.

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