Sérgio Lifschitz

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In this work we investigate the parallel evaluation of BLAST, the most popular tool for comparing biological sequences. Our goal is to study database distribution issues that, besides workload balancing, could improve the performance of a set of BLAST processes running in a workstation cluster. We consider different partitioning strategies within actual(More)
It has been important to extend database management systems to support new requirements of applications and administration. We focus in this paper on the automatic tuning feature, particularly manipulation of indexes. The architectural approach considered here is based on software agents. We briefly present the heuristics involved in the decision upon(More)
The use of software agents as Database Management System components lead to database systems that may be configured and extended to support new requirements. We focus here with the self-tuning feature, which demands a somewhat intelligent behavior that agents could add to traditional DBMS modules. We propose in this paper an agent-based database(More)
Mobile computing allows for the development of new and sophisticated database applications. Such applications require the reading of current and consistent data. In order to improve data availability, increase performance and maximize throughput, data replication is used. However, due to inherent limitations in mobile and other loosely-coupled environments,(More)
We study a dose-driven dynamic load balancing strategy to evaluate database recursive queries. This proposal aims at obtaining a good workload balance with full use of the available resources, with different kinds of skew considered. The strategy is intended for general recursive queries and preliminary computational results illustrate its ef-ciency when(More)
Automatic index selection has received significant attention in the au-tonomic computing field. Previous works have focused on providing tools and algorithms to help the DBA in the choice of indices for a given static workload. We present an approach for indexing management that works for workloads that may dynamically change with no human intervention at(More)
We present algorithms for computing some distance functions between two (possibly intersecting) polygons, both in the convex and nonconvex cases. The interest for such distance functions comes from applications in robot vision, pattern recognition and contour fitting. We present a linear sequential algorithm and an optimal EREW·PRAM parallel algorithm for(More)