What is Schema Evolution

In information systems, changing the database schema is a common but often troublesome task in database administration that is needed for many reasons such as changes in user requirements, compliance to new regulations, addition of new functionalities, or correction of deficiencies in the current schema. For most database applications, changing the schema of the database without loss of existing data is a significant challenge: it is usually a time-consuming and error-prone task which must be done carefully. In the literature, schema evolution has been defined as the modality for the management of schema changes which relieves database programmers and administrators from this burden, by automatically recovering extant data and possibly adapting them to the new schema. The main goal of this chapter is to present the recent research proposals that deal with schema evolution in traditional and emerging databases and to discuss the recent advances on schema evolution support in mainstream DBMSs.