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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 re 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(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)
Most semantic data models and object-oriented data models allow entity and object classes to be organized according to a generalization taxonomy. In addition, range restrictions (or property typing) may be specified not only on properties associated with a given class, but also on properties inherited from superclasses. In this paper, we consider a more(More)