The eXtensible Markup Language (XML) is a key technology that facilitates both information exchange and e-business transactions. Starting with DB2 UDB Net.Data VI, an application can generate XML documents from SQL queries against DB2 or any ODBC compliant databases. Today DB2 UDB XML Extender not only serves as a repository for both XML documents and their Document Type Definitions (DTDs), but also provides data management functionalities such as data integrity, security, recoverability and manageability. The user has the option to store the entire document as an XML user-defined column or to decompose the document into multiple tables and columns. Fast search via indices is provided for both XML elements and attributes. Section search can be done against the content of the document. Query syntax adheres to W3C standards such as Extensive Stylesheet Language Transformation (XSLT) and XML Path Language (XPath) specifications. The user can retrieve the entire document or extract XML elements and attributes dynamically in an SQL query. In addition, XML Extender provides a stored procedure to generate XML documents from existing data. Together with Net.Data, one can browse the content of the XML documents via the Internet.

HTML has so far been the standard format for delivering information on the World Wide Web. However, automated information processing of these documents for data exchange and interoperability has been difficult. XML, a subset of SGML, has been proposed to be the next standard format, that allows user-defined tags for better describing nested document structures and associated semantics. Operations on structured documents, such as searching in nested document structures, require new functions that are not currently available on most systems today. We describe a general framework for manipulating structured documents based on document abstractions. An abstraction is an approximation of an actual document, while possessing useful properties for analyses of interest. The framework provides a wide design space for the tradeoff between cost and capability. This general framework can be applied to index design, document searching and categorization. We present this framework by focusing on the indexing and searching of structured documents in the XML domain, and prove their soundness. We also address the issue of rich data types in XML documents.