In federated database systems(FDBS) context, providing a functional mechanism for global schema evolution is very important to preserving overall consistent states over time and servicing new informations for global users.
In this thesis, we propose a methodology for global schema update that is a basic mechanism for schema evolution in FDBS whose global schema has been created based on object merging methods. In order to handle changes of local schema, first, we investigate types of local schema change that can be occurred in FDBS and classify these two categories. Second, we define schema integration tree(SIT) and its meta data structure to provide working environment to the methodolgy. Lastly we introduce an object-detach function that is essential to object removal.
The proposed methodology will be well adapted to existed FDBS with minimal modification because its framework can be naturally constructed through integration process and functions involved in it are based on the same methodology that schema integration used. And some of proposed methodology can cover incremental processing of schema integration that others do not consider without re-integration.
