As explained in the introduction of this chapter, SOAP stands for Simple Object Access Protocol. It is a standard that defines how the message that calls the web service should be defined and how the answer is returned. Both messages are in XML.
SOAP web services can be defined in so called Web Service Description Language (WSDL) documents. By reading a WSDL, an application knows what web services are available, how to call them, and what response it can expect back. APEX uses the information in a WSDL document to generate the SOAP messages, without the developer having to do any programming.
In this recipe we are going to show how we can call an SOAP web service using built-in functionality of Application Express.