Data schema evolution support in XML-relational database systems

Many XML-relational systems, i.e., the systems that use an XML schema as an external schema and a relational schema as an internal schema of the data application representation level, require modifications of the data schemas in the course of time. Schema evolution is one of the ways to support schema modifications for the application at the DBMS level. A number of schema evolution support systems for different data models have been suggested. Schema evolution can be applied to mapping-related evolving schemas (such as schemas of XML-relational systems), the transformation problem for which is also known as schema adaptation. In this paper, a survey of various approaches to solving the outlined problems is given.