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The problem of answering queries using views is to find efficient methods of answering a query using a set of previously materialized views over the database, rather than accessing the database relations. The problem has recently received significant attention because of its relevance to a wide variety of data management problems. In query optimization,(More)
Many problems encountered when building applications of database systems involve the manipulation of models. By “model,” we mean a complex structure that represents a design artifact, such as a relational schema, object-oriented interface, UML model, XML DTD, web-site schema, semantic network, complex document, or software configuration. Many uses of models(More)
Information integration systems, also knows as mediators, information brokers, or information gathering agents, provide uniform user interfaces to varieties of di erent information sources. With corporate databases getting connected by intranets, and vast amounts of information becoming available over the Internet, the need for information integration(More)
A data-integration system provides a uniform interface to a multitude of data sources. Consider a data-integration system providing information about movies from data sources on the World Wide Web. There are numerous sources on the Web concerning movies, such as the Internet Movie Database (which provides comprehensive listings of movies, their casts,(More)
Speeding up inferences made from large knowledge bases is a key to scaling up knowledge based systems. To do so, a system must have the ability to automatically identify and ignore information that is irrelevant to a speci c task. Identifying irrelevant knowledge is also key to enabling reasoning in environments in which several systems (and their(More)