Authors:
Cecilia Delgado
1
;
José Samos
1
and
Manuel Torres
2
Affiliations:
1
Universidad de Granada, Spain
;
2
Universidad de Almería, Spain
Keyword(s):
Schema Evolution, Object-Oriented Databases, External Schemas, Schema Changes.
Related
Ontology
Subjects/Areas/Topics:
Databases and Information Systems Integration
;
Enterprise Information Systems
;
Object-Oriented Database Systems
Abstract:
Schema evolution is the process of applying changes to a schema in a consistent way and propagating these changes to the instances while the database is in operation. However, when a database is shared by many users, updates to the database schema are always difficult. To overcome this problem, in this paper we propose a version mechanism for schema evolution in ODMG databases that preserves old schemas for continued support of existing programs running on the shared database when schema changes are produced. Our approach uses external schema definition techniques and is based on the fact that if a schema change is requested on an external schema, rather than modifying the schema, a new schema, which reflects the semantics of the schema change, is defined.