Using XML to integrate existing software systems into the Web

The eXtensible Markup Language (XML) is not only a language for communication between humans and the Web, it is also a language for communication between programs. Rather than passing parameters, programs can pass documents from one to another, containing not only pure data, but control information as well. Even legacy programs written in ancient languages such as COBOL and PL/I can be adapted by means of interface reengineering to the process and to generate XML documents. This paper intends to describe the process and the tools required to accomplish that goal and to present three cases - one for online, one for batch and one for subprograms - to illustrate how XML may be used to integrate existing software systems into the Web.