Primitive Operations for Schema Evolution in ODMG Databases

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. In this process there are two problems to consider: semantics of change and change propagation. In this paper, we study the problem of the semantics of change for the schema evolution defined with the ODMG object model. In this context, we provide a formal definition of this object model, we establish a set of axioms to ensure the consistency of a schema when it is modified, and we define a set of primitive operations that allow basic changes to be carried out on an ODMG schema. Other operations, which allow any kind of modification to be carried out, can be derived from these primitives.