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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)
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)
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)
From beginning of 1994 to the end of 1996, the IRO-DB ESPRIT project has developed tools for accessing relational and object-oriented databases in an integrated way. The system is based on the ODMG standard as pivot model and language. It consists of three layers. The local layer provides for an ODMG interface to heterogeneous DBMSs, the communication layer(More)
The purpose of this paper is to present an approach for verifying that explicitely stated integrity constraints are not violated by certain transactions. We utilize a relational model where-in constraints are given in a language based on the first order predicate calculus. Transactions are written in terms of an ALGOL.60 like host language with embedded(More)