Querying XML effectively and efficiently using declarative languages such as XQuery and XPath has been widely studied in both academic and industrial settings. Most RDBMS vendors now support XML as a native data type with SQL/XML and XQuery support over it. However, the problem of updating XML is still the subject of ongoing effort. Several SQL/XML update extensions have been implemented and an XQuery Update Facility is in the proposal phase to add an update capability to XQuery. There are a lot of challenges involved in updating XML, particularly identifying and updating partial fragments of XML while maintaining concurrency, transactional semantics and validity of the document. In this paper, we illustrate the XML update functionality provided by Oracle XML DB within the context of SQL/XML. This functionality has been developed and optimized based on actual customer use cases of querying and updating XML. We discuss our design philosophy, optimization details for providing capability of updating XML and compare it with the current XQuery Update Facility proposal with the goal of providing insight into incorporating the XQuery Update Facility in the SQL/XML standard in the future.

XML has become an attractive data processing model for applications. SQL/XML is a SQL standard that integrates XML with SQL. It introduces the XML datatype as a native SQL datatype and defines XML generation functions in the SQL/XML 2003 standard. The goal for the next version of SQL/XML is integrating XQuery with SQL by supporting XQuery embedded inside SQL functions such as the XMLQuery and XMLTable functions. Starting with the 9i database release, Oracle has supported the XML datatype and various operations on XML instances. In this paper, we present the design and implementation strategies of the SQL/XML standard in Oracle XMLDB. We explore the various critical infrastructures needed in the SQL database kernel to support an efficient native XML datatype implementation and the design approaches for efficient generation, query and update of the XML instances. Furthermore, we also illustrate extensions to SQL/XML that makes Oracle XMLDB a truly industrial strength platform for XML processing.