Integrated Querying of XML Data in RDBMSs

This paper proposes a way to integrate cleanly relational databases and XML documents. The main idea is to draw a clear line of demarcation between the two concepts by modelling XML documents as a new atomic SQL type. The standardised XML tools like XPath, XQuery, XSLT are then user-defined functions that operate on this type. Well-defined interoperability is guaranteed by, on the one hand, defining a standard way to markup SQL relations as XML documents and, thus, to make them accessible to the XML tools; on the other hand, XPath and XQuery queries run against the XML portion of the database can use the same predefined schema to make their results accessible to the SQL language for further processing. Additionally, a method for set-oriented evaluation of regular path expressions is presented that integrates into our implementation framework.