Schema evolution in object oriented databases using virtual interface Objects

摘要

In RDBMS, it is the schema that is usually considered to be stable and therndata that changes. However schemas are not constant, as we would expect. Sincernthe role of a database is to model a part of the real world, if the part that is to bernmodeled changes in structure, then the database structure i.e. the schema mustrnchange. Especially the next generation applications such as Computer aidedrndesign (CAD), Computer aided manufacturing (CAM) and multimediarninformation system, where object oriented database (OODB) is used, requiresrnfrequent schema changes. Further more a database designer, like all designers arernprone to make mistakes and may be failing to identify all the data modelingrnrequirements of a database. To correct such mistakes, the schema must bernmodifiable. But when many users share a database, changes to the databasernschema are almost prohibited because there is a risk of making existing applicationrnprograms obsolete when they run against the modified schema. It requires arnsolution, so that the schema is allowed to change and at the same time existingrnapplications continue to work against the redefined schema. This paper describes arnsolution approach for Schema evolution in OODB using virtual interface objects.