The Simple Object Access Protocol (SOAP) procedure reads XML input from a file that has a fileref and writes XML output to another file that has a fileref. The message component, an XML document that corresponds to a service request, is part of the content of the fileref. It is defined in the IN option of PROC SOAP. The input XML is either a SOAPEnvelope element, or an element inside the SOAPEnvelope that is required to invoke the Web service.