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Consider a database containing not only base relations but also stored derived relations (also called materialized or concrete views). When a base relation is updated, it may also be necessary to update some of the derived relations. This paper gives sufficient and necessary conditions for detecting when an update of a base relation cannot affect a derived(More)
In virtually every organization, data is stored in a variety of ways and managed by diierent database and le systems. Applications that require data from multiple sources are complex because they must be aware of and deal with the speciics of each data source. They must also perform any data integration needed, for example, joining data from multiple(More)
Multidatabase systems provide integrated access to autonomous, distributed, and heterogeneous database systems. As such they provide a core technology for Cooperative Information Systems. One of the main issues in developing multidatabase systems is that of managing global information such as properties of component sites and databases, component and(More)