A Semantic Network-Based Design Methodology for XML Documents

The Extensible Markup Language (XML) is fast emerging as the dominant standard for describing and interchanging data among various systems and databases on the Internet. It offers the Document Type Definition (DTD) as a formalism for defining the syntax and structure of XML documents. The XML Schema definition language, as a replacement for the DTD, provides more rich facilities for defining and constraining the content of XML documents. However, it does not concentrate on the semantics that underlies these documents, representing a logical data model rather than a conceptual model. To enable efficient business application development in large-scale electronic commerce environments, it is necessary to describe and model real-world data semantics and their complex interrelationships. In this article, we describe a design methodology for XML documents. The aim is to enforce XML conceptual modeling power and bridge the gap between software development and XML document structures. The proposed methodology is comprised of two design levels: the semantic level and the schema level. The first level is based on a semantic network, which provides semantic modeling of XML through four major components: a set of atomic and complex nodes, representing real-world objects; a set of directed edges, representing semantic relationships between the objects; a set of labels denoting different types of semantic relationships, including aggregation, generalization, association, and of-property relationships; and finally a set of constraints defined over nodes and edges to constrain semantic relationships and object domains. The other level of the proposed methodology is concerned with detailed XML schema design, including element/attribute declarations and simple/complex type definitions. The mapping between the two design levels is proposed to transform the XML semantic model into the XML Schema, based on which XML documents can be systematically created, managed, and validated.