Superviews: Virtual Integration of Multiple Databases

An important advantage of a database system is that it provides each application with a custom view of the data. The issue addressed in this paper is how to provide such custom views to applications that access multiple databases. The paper describes a formal method that generates such superviews, in an interactive process of schema editing operations. A mapping of the superview into the individual databases is derived from the editing process, and is stored together with the superview as a virtual database. When this database is interrogated, the mapping is used to decompose each query into a set of queries against the individual databases, and recompose the answers to form an answer to the original query. As this process is transparent to the user, virtual databases may be regarded as a more general type of databases. A prototype database system, that allows users to construct virtual databases and interrogate them, has been developed.