Oliver M. Duschka

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Infomaster is an information integration system that provides integrated access to multiple distributed heterogeneous information sources on the Internet, thus giving the illusion of a centralized, homogeneous information system. We say that Infomaster creates a virtual data warehouse. The core of Infomaster is a facilitator that dynamically determines an(More)
Generating query-answering plans for data integration systems requires to translate a user query, formulated in terms of a mediated schema, to a query that uses relations that are actually stored in data sources. Previous solutions to the translation problem produced sets of conjunctive plans, and were therefore limited in their ability to handle recursive(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)
Generating query-answering plans for information gathering agents requires to translate a user query, formulated in terms of a set of virtual relations, to a query that uses relations that are actually stored in information sources. Previous solutions to the translation problem produced sets of conjunctive plans, and were therefore limited in their ability(More)
Infomaster is an information integration system. It provides integrated access to distributed, heterogeneous information sources, thus giving its users the illusion of a centralized, homogeneous information system. Infomaster is the rst such system that is able to handle arbitrary positive relational algebra user queries and database descriptions. It is(More)
We consider the problem of query plan optimization in information brokers. Information brokers are programs that facilitate access to collections of information sources by hiding source-speciic peculiarities and presenting uniform query interfaces. It is unrealistic to assume that data stored by information sources is complete. Therefore, current(More)