DB2 provides native XML storage, indexing, navigation and query processing through both SQL/XML and XQuery using the XML data type introduced by SQL/XML. In this tutorial we focus on DB2's XML support for schema evolution, especially DB2's schema repository and document-level validation.

This paper describes the overall architecture and design aspects of a hybrid relational and XML database system called System RX. We believe that such a system is fundamental in the evolution of enterprise data management solutions: XML and relational data will co-exist and complement each other in enterprise solutions. Furthermore, a successful XML repository requires much of the same infrastructure that already exists in a relational database management system. Finally, XML query languages have considerable conceptual and functional overlap with relational dataflow engines. System RX is the first truly hybrid system that comingles XML and relational data, giving them equal footing. The new support for XML includes native support for storage and indexing as well as query compilation and evaluation support for the latest industry-standard query languages, SQL/XML and XQuery. By building a hybrid system, we leverage more than 20 years of data management research to advance XML technology to the same standards expected from mature relational systems.

Relational queries on continuous streams of data are the subject of many recent database research projects. In 1998 a small group of people started a similar project with the goal to transform our product, NonStop SQL/MX, into an active RDBMS. This project tried to integrate functionality of transactional queuing systems with relational tables and with SQL, using simple extensions to the SQL syntax and guaranteeing clearly defined query and transactional semantics. The result is the first commercially available RDBMS that incorporates streams. All data flowing through the system is contained in relational tables and is protected by ACID transactions. Insert and update operations on any NonStop SQL table can be considered publishing of data and can therefore be transparent to the (legacy) applications performing them. Unlike triggers, the publish operation does not increase the path length of the application and it allows the subscriber to execute in a separate transaction. Subscribers, using an extended SQL syntax, see a continuous stream of data, consisting of all rows originally in the table plus all rows that are inserted or updated thereafter. The system scales by using partitioned tables and therefore partitioned streams.