SOAP is a protocol used to format message exchanges between Web service clients and Web services. The industry currently considers many scenarios for Web services communications (described at http://www.w3.org/TR/ws-arch-scenarios/). OpenEdge supports the request-response scenario.

In the request-response scenario, a client (Web service client) sends a SOAP request message to invoke a Web service operation on the Web service provider and the provider sends a response back to the client in the form of a SOAP response message (for a successful invocation) or in the form of a SOAP fault message (for an invocation that results in an error).

Given the automated resources available for producing and consuming Web services, you might not need to understand much about SOAP messages. The following sections give a brief overview of SOAP messages.