These applications co-exist with or replace their more expensive EDI cousins. XML converts the Web into a huge database where programs, not people, can go to find the needed information. The concept of Web services was just introduced last year. In its most simplistic terms, a Web service is a program with input and output parameters that is made available for others to execute across the Web. In RPG, the CALL and PARM op codes describe the interface between the two program objects.
SOAP provides a similar program-calling interface.
The difference is that SOAP is platform independent and works across the Web. With SOAP, it's possible to publish interfaces to your system's internal programs and have them callable across the Web. Applications built for this fourth stage will be distributed with some parts of the application running on your machine and others running on customers', suppliers', and business partners' machines. A simple example of a Web service would be one provided by a shipping and delivery company. Companies such as FedEx already provide Web pages that perform this type of calculation, but they require lots of manual user input.