Rules about XML in XML

We developed three different rule-based systems, each designed to take XML as input and produce XML as output and manipulate intermediate facts as XML. They use very different methods of representing the XML during rule processing. Our series of benchmarks show when each representation is best. We also developed an XML language for representing the rules. The markup to recognize an input XML is a sample of that input; certain fields are replaced with special tags to match variables against text or subtrees within the input XML. The output or intermediate XML is also represented by a sample of the output XML. We also report on a graphical user interface developed for developing the rules in this special XML language.