XML and Relational Database Systems — A Comparison of Concepts

Database systems are well-known for consistent storage, retrieval, and manipulation of data. At the same time, the Extensible Markup Language (XML) is generally accepted as data description language for both web-based information systems and electronic data interchange between different organizations. Since database systems form the backbone of essentially any information system, the integration of XML and database systems is a must. Data model heterogeneity and schema heterogeneity, however, makes this a challenging task, for example when mapping XML documents to relational database systems (RDBS). This paper focuses on data model heterogeneity and provides an in-depth comparison of concepts available in RDBS and XML schema specification languages, comprising XML DTD and XML Schema. Such an analysis provides the basis for developing appropriate middleware bridging the gap between XML and RDBS.