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)
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)
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)
This work presents the core ideas for an approach that enables index tuning with no human intervention at all. SQL statements submitted to the database are monitored and indices are created or dropped according to the benefits or overheads regarding the actual workload. We have implemented this strategy using a software agent architecture embedded in(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)
Knowledge representation in the biological domain suffers from two main difficulties that make it hard to apply traditional conceptual modeling tools: the inherent domain complexity and its constant evolution. The former requires complex types and associations, whereas the latter calls for an expressive language. We list in this paper a set of requirements(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)