The CORDS multidatabase project

In virtually every organization, data are stored in a variety of ways and managed by different database and file systems. Applications requiring data from multiple sources must recognize and deal with the specifics of each data source and must also perform any necessary data integration. The objective of a multidatabase system is to provide application developers and end users with an integrated view of and a uniform interface to all the required data. The view and the interface should be independent of where the data are stored and how the data are managed. CORDS is a research project focused on distributed applications. As part of this project, we are designing and prototyping a multidatabase system. This paper provides an overview of the system architecture and describes the approaches taken in the following areas: management of catalog information, schema integration, global query optimization, (distributed) transaction management, and interactions with component data sources. The prototype system gives application developers a view of a single relational database system. Currently supported component data sources include several relational database systems, a hierarchical database system, and a network database system.