Semantic extensions of XML for advanced applications

XML is a de facto standard for structuring documents and their exchange in electronic forms. However it has many restrictions to represent various information from viewpoints of data-centered applications. Set and tuple constructors are useful for defining data structure, and identities and user views are indispensable for sharing common data, while XML, even with XML Schema, does not support such features. In this paper, we propose an approach to semantic extensions of XML by introducing some special attributes, by which conventional data constructors can be utilized and semantic elements for user views can be defined. Along this approach, we have been developing XML-based systems for heterogeneous document management, digital theme parks, and interactive multimedia presentation, where there are many enhancement requests to XML. We discuss the effectiveness of extensions by taking examples in our applications.

1 Introduction

XML is a de facto standard as a markup language for structuring documents and their exchange in electronic forms, and its applications such as SVG, X3D, VoiceXML, and SMIL have been developed to capture more multimedia information. However, as application areas are enlarging, we encounter more restrictions of XML for coping with various requirements. For example, in XML, we cannot use conventional data constructors such as set and tuple constructors, and object identities, for embedding database information into XML. Further, the data structure (well-formedness) of XML is too narrow for describing various information such as circular or overlapped data, and semantic hyper-structure. In this paper, we discuss semantic extensions of XML for coping with advanced applications with the above requirements. As HyTime[7] is a semantic extension of SGML for treating multimedia information, our approach seems to be similar with it but our target is different from it.