Distributed data integration by object-oriented mediator servers

Integration of data from autonomous, distributed and heterogeneous data sources poses several technical challenges. This paper overviews the data integration system AMOS II based on the wrapper-mediator approach. AMOS II consists of: (i) a mediator database engine that can process and execute queries over data stored locally and in several external data sources, and (ii) object-oriented (OO) multi-database views for reconciliation of data and schema heterogeneities among sources with various capabilities. The data stored in different types of data sources is translated and integrated using OO mediation primitives, providing the user with a consistent view of the data in all the sources. Through its multi-database facilities many distributed AMOS II systems can interoperate in a federation. Since most data reside in the data sources, and to achieve high performance, the core of the system is a main-memory DBMS having a storage manager, query optimizer, transactions, client-server interface, disk backup, etc. The AMOS II data manager is optimized for main-memory access and is extensible so that new data types and query operators can be added or implemented in some external programming language. The extensibility is essential for providing seamless access to a variety of data sources.