Client requests and web service responses are transmitted as Simple Object Access Protocol (SOAP) messages over HTTP to enable a completely interoperable exchange between clients and web services, all running on different platforms and at various locations on the Internet. HTTP is a familiar request-and response standard for sending messages over the Internet, and SOAP is an XML-based protocol that follows the HTTP request-and-response model.
The SOAP portion of a transported message handles the following:
Defines an XML-based envelope to describe what is in the message and how to process the message
Includes XML-based encoding rules to express instances of application-defined data types within the message
Defines an XML-based convention for representing the request to the remote service and the resulting response