The XML Expert System Shell (XESS) was designed to alleviate some of the difficulties associated with
translating a knowledge base from one expert system to another. The major goal of XESS is to allow
programmers to model an expert system, complete with traditional facts and rules, in an XML-based
language that leverages the universally understood terms used when teaching artificial intelligence to
students. XML, the extensible markup language, is a text-based standard for information interchange
between disparate systems1; it was originally designed to represent data in an easily parsable, human
readable format2. While some extensions of the XML specification, particularly the Simple Object Access
Protocol (SOAP), have long since abandoned human readability, the core XML specification is still used
frequently to produce documents that can easily be exchanged between computational platforms and
created or understood by human beings. The XESS-XML language inherits all of the usability of XML; it
can be edited by hand in any text editor, is human readable, and can be parsed using XML parsers
commonly available in any modern programming language.
The XML Schema specification provides a mechanism for explicitly defining the content of an XML
document so that a document can be validated3...