F2-XML: Managing XML document schema evolution

Abstract

XML has become an emerging standard for data representation and data exchange on the Web. Although XML data is self-describing, most application domains tend to use document schemas. Over a period of time, these schemas need to be modified to reflect a change in the real-world, a change in the user's requirements, mistakes or missing information in the initial design. Most of the current XML management systems do not support schema changes. In this paper, we propose the F2-XML method to manage XML document schema evolution. We consider XML documents associated with DTDs, Our method consists in three steps. First, the DTD and XML documents are stored as a database schema and a database instance respectively. Second, DTD changes are applied as schema changes on the database. Third, the updated DTD and XML documents are retrieved from the database. Our method supports a complete set of DTD changes. The semantics of each DTD change is defined by preconditions and postactions, such that the new DTD is valid, existing XML documents conform to the new DTD, and data is not lost if possible. We implemented our method in the F2 object-oriented database system. XML, schema evolution, object-oriented database system.