Based on the requirements, SOAP is an obvious choice as base technology for the exposed API. Figure 15.1 shows the high-level structure of the application in relation to potential external clients.
Figure 15.1. Public order processing system high-level overview.
SOAP is an XML-based Remote Procedure Call protocol that was originally intended to be served via HTTP requests. Each SOAP request is logically mapped to a method invocation on a server object. The object processes the arguments that were passed in by the SOAP client, then sends a result that the client reads as an HTTP response.
Like HTTP, SOAP calls are ...