A schema version model for complex objects in object-oriented databases

In this paper, we propose a schema version model which allows to restructure complex object hierarchy in object-oriented databases. This model extends a schema version model, called RiBS, which is based on the concept of Rich Base Schema. In the RiBS model, each schema version is in the form of updatable class hierarchy view over one base schema, called the RiBS layer, which has richer schema information than any existing schema version in the database. In this paper, we introduce new operations for restructuring composite object hierarchy in schema versions, and explain their semantics. We also touch upon the ways to transform queries posed against a restructured composite object hierarchy into one against the base schema. In addition, we identify several types of conflicts during schema version merging which result from the restructuring operations, and provide a semi-automatic algorithm to resolve the conflicts. The originality of this paper lies in that (1) we introduce several new operations to restructure composite object hierarchy, and (2) this extended RiBS model operations raise the concept of data independence in OODBs upto the schema level. (c) 2006 Elsevier B.V. All rights reserved.