Abstract

With XQuery becoming the standard language for querying XML, and the relational SQL platform being recognized as an important platform to store and process XML, the SQL/XML standard is integrating XML query capability into the SQL system by introducing new SQL functions and constructs such as XMLQuery() and XMLTable. This paper discusses the Oracle XMLDB XQuery architecture for supporting XQuery in the Oracle ORDBMS kernel which has the XQuery processing tightly integrated with the SQL/XML engine using native XQuery compilation, optimization and execution techniques.

No abstract

XML is here as the internet standard for information exchange among e-businesses and applications. With its dramatic adoption and its ability to model structured, unstructured and semi-structured data, XML has the potential of becoming the data model for internet data. In the recent years, Oracle has evolved its DBMS to support complex, structured, and un-structured data. Oracle has now extended that technology to enable the storage and querying of XML data by evolving its DBMS to an XML enabled DBMS -Oracle8i.In this paper, we will present Oracle's XMLenabling database technology. In particular, we will discuss how XML data can be stored, managed, and queried in the Oracle8i database.

Oracle XML DB integrates XML storage and querying using the Oracle relational and object relational framework. It has the capability to physically store XML documents by shredding them as relational or object relational data, and creating logical XML documents using SQL/XML publishing functions. However, querying XML in a relational or object relational database poses several challenges. The biggest challenge is to efficiently process queries against XML in a database whose fundamental storage is table-based and whose fundamental query engine is tuple-oriented. In this paper, we present the 'XML Query Rewrite' technique used in Oracle XML DB. This technique integrates querying XML using XPath embedded inside SQL operators and SQL/XML publishing functions with the object relational and relational algebra. A common set of algebraic rules is used to reduce both XML and object queries into their relational equivalent. This enables a large class of XML queries over XML type tables and views to be transformed into their semantically equivalent relational or object relational queries. These queries are then amenable to classical relational optimisations yielding XML query performance comparable to relational. Furthermore, this rewrite technique lays out a foundation to enable rewrite of XQuery [1] over XML.