Once such database has been created, the sources are discarded and the conceptual level is not used anymore. The setting of multidatabases deals with different sources, which are considered as internal components of the Integration System. A. Hurson, M. Bright, and S. Pakzad, editors. An Advanced Solution for Global Information Sharing . IEEE Computer Society Press, 1994.
Information integration can be either virtual or materialized.
In virtual integration query answering is generally costly, because it requires accessing the sources. Once such database has been created, the sources are discarded and the conceptual level is not used anymore. The setting of multidatabases deals with different sources, which are considered as internal components of the Integration System. A. Hurson, M. Bright, and S. Pakzad, editors. An Advanced Solution for Global Information Sharing .