Marcos Sfair Sunyé

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This paper describes an implementation of Kruskal's algorithm in query optimization process for generation of a near optimal execution query tree. The open source Post- greSQL DBMS was used in the experiments since its query optimization is performed by dynamic programming and genetic algorithm, which allows a concrete comparison with our approach.(More)
The importance of digital information is constantly increasing in the last years. Such information often needs to be preserved for a long-term and this is the responsibility of digital archiving systems. This paper proposes a reliable replication model of immutable digital content to be used in long-term archiving systems. The archiving system is modeled as(More)
Often in a competitive market, corporations need tools to increase the accuracy and efficiency of the decisions. Facing this, several companies that have no resources to buy the commercial systems available because of the high costs, have no chance to buy a Decision Support Systems (DSS) platform. This paper is dedicated to a benchmark of PostgreSQL DBMS(More)
Open archives initiative (OAI) allows both libraries and museums create and share their own low-cost digital libraries (DL). OAI DL are based on OAI-PMH protocol which, although is consolidated as a pattern for disseminating metadata, does not rely on either digital preservation and availability of content, essential requirements in this type of system.(More)
In relational database model, the use of exhaustive search methods in the large join query optimization is prohibitive because of the exponential increase of search space. An alternative widely discussed is the use of randomized search techniques. Several previous researches have been showed that the use of randomized sampling in query optimization permits(More)
This paper describes an interface and interaction environment for a public online Chess server, on the web, as an educational tool. The main purpose of the environment is to improve Chess teaching in Brazilian public schools. The vast majority of such Chess online servers consider and take for granted that users are specialists rather than learners. The(More)