An Equivalent-Tranformation-Based XML Rule Language

This paper proposes XML Equivalent Transformation (XET) as an XML-based rule langauge for the Web, which seamlessly integrates human-readable documents and computer-interpretable programs by considering XML documents and XML expressions—an extension of ordinary XML elements with variables—as its first class programming entities. With XET, arbitrary XML documents, representing application data, information or knowledge on the Web possibly encoded in certain XML applications, become immediately a program’s input data. Manipulation and computation of such an input document (data) is performed by semantically-equivalently transforming the document successively until a desirable one is obtained. The input document could be, for example, an XML database query, and thus the output or the desirable document is a set of XML elements yielding the answer to the query. The paper presents the syntax and the computation mechanism of XET and also demonstrates its application to e-business systems.