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Distributed systems require declarative access to diverse information sources. One approach to solving this heterogeneous distributed database problem is based on mediator architectures. In these architectures, mediators accept queries from users, process them with respect to wrappers, and return answers. Wrapper provide access to underlying sources. To(More)
Providing integrated access to multiple, distributed and heterogeneous data sources has become one of the major issue in database research and industry. Being a major European Esprit project started in 1993, IRO-DB is experimenting an on-demand solution to this problem. IRO-DB is an object-oriented federated database system to access multiple data sources(More)
Query processing is one of the most, critical issues in Object-Oriented DBMSs. Extensible opt,imizers with efficient, search strategies require a cost model to select the most efficient execution plans. In this paper we propose and partially validate a generic cost-model for Object-Oriented DBMSs. The storage model and its access methods support clus-t,ered(More)
Discovery of association rules is an important problem in Data Mining. The classical approach is to generate all itemsets that have support (i.e., the fraction of transactions containing the itemset) above a user given threshold. Most existing algorithms aim at reducing the number of scans over the transaction database, i.e., the I/O overhead. We consider(More)
XML has emerged as the leading language for representing and exchanging data not only on the Web, but also in general in the enterprise. XQuery is emerging as the standard query language for XML. Thus, tools are required to mediate between XML queries and heterogeneous data sources to integrate data in XML. This paper presents the XMedia mediator, a unique(More)
Several federated database systems have been built in the past using the relational or the object model as federating model. This paper gives an overview of the XMLMedia system, a federated database system mediator using XML as federating model, built in the Esprit Project MIRO-Web. The system is composed of four main components: a wrapper generator using(More)
This paper presents and analyzes algorithms for computing joins and semijoins of relations in a multiprocessor database machine. First, a model of the multiprocessor architecture is described, incorporating parameters defining I/O, CPU, and message transmission times that permit calculation of the execution times of these algorithms. Then, three join(More)