SCHEMA INTEGRATION AND TRANSACTION MANAGEMENT FOR MULTIDATABASES

In this paper we propose a schema integration technique to integrate m ultiple autonomous database systems. We adopt the unified model, which is basically a relational model with object-oriented features, as the global model for integrating schemas of multiple database in the rela tional, hierarchical, network, and object-oriented models. The feature s and the advantages of the unified model as the global model are disc ussed, then we describe the methodologies to integrate heterogeneous d atabases using this model and show how various types of conflicts are resolved. We also show how a global query on the integrated schema is handled in heterogeneous environment. We also present a transaction ma nagement scheme which uses semantic recovery techniques. Our scheme do es not impose any restrictions on data items that transactions can rea d and write and does not violate local autonomy. (C) 1998 Elsevier Sci ence Inc. All rights reserved.