Subquery Allocation Problem and Heuristics for Secret Sharing Distributed Database System

We discuss query optimization in a secure distributed database system, called the Secret Sharing Distributed DataBase System (SSDDBS). We have to consider not only subquery allocations to distributed servers and data transfer on the network but also decoding distributed shared data. At first, we formulated the subquery allocation problem as a constraints satisfaction problem. Since the subquery allocation problem is NP-complete in general, it is not easy to obtain the optimal solution in practical time. Secondly, we proposed a heuristic evaluation function for the best-first search. We constructed an optimization model on an available optimization software, and evaluated the proposed method. The results showed that feasible solutions could be obtained by using the proposed method in practical time, and that quality of the obtained solutions was good

Estrategia de procesamiento y optimización de consultas en un gestor de bases de datos federadas

Based on BLOOM (BarceLona Object-Oriented Model), we propose to establish a global query processing strategy in the Federated Query Manager. First, the developing mechanism constructs a tree, which has nodes that initially represent explicit joins between federated classes and that are decomposed, into implicit joins between classes in the Component Schemas. Consequently, different heuristic techniques are performed in order to optimise the decomposition process, which generate one or more Execution Plans (EP). After that, the EP are analysed to get the optimum. The objective function of this strategy is to choose an execution plan with the least total resource usage and the best response time. Finally, the consolidation of partial results is carried out maintaining the federated result in the root node.Basado en el Proyecto BLOOM (BarceLona Object- Oriented Model), se propone establecer una estrategia de procesamiento de la consulta global dentro del Gestor de Consultas Federado. Primero, se construye un árbol cuyos nodos inicialmente representan joins explícitos entre clases federadas y los cuales son descompuestos en joins implícitos entre clases en los esquemas componentes. Posteriormente, diferentes técnicas heurísticas optimizan el proceso de descomposición, las cuales generan uno o mas Planes de Ejecución (PE). Después, éstos PE son analizados para obtener el optimo. La función objetiva de esta estrategia es encontrar un plan de ejecución con el menor uso de recursos y el mejor tiempo de respuesta. Finalmente, la consolidación de resultados parciales se lleva a cabo manteniendo la respuesta federada en el nodo raíz.Postprint (published version

Robust Query Optimization Methods With Respect to Estimation Errors: A Survey

International audienceThe quality of a query execution plan chosen by a Cost-Based Optimizer (CBO) depends greatly on the estimation accuracy of input parameter values. Many research results have been produced on improving the estimation accuracy, but they do not work for every situation. Therefore, "robust query optimization" was introduced, in an effort to minimize the sub-optimality risk by accepting the fact that estimates could be inaccurate. In this survey, we aim to provide an overview of robust query optimization methods by classifying them into different categories, explaining the essential ideas, listing their advantages and limitations, and comparing them with multiple criteria

Ontologies, contexts, and mediation : representing and reasoning about semantics conflicts in heterogeneous and autonomous systems

Cover title.Includes bibliographical references (p. 35-37).Cheng Hian Goh, Stuart E. Madnick, Michael D. Siegel

Banco de dados distribuídos para auxiliar na gerência de redes

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação.Atualmente a maioria das empresas de médio e grande porte formadas de filiais que geralmente se localizam geograficamente distantes entre si não possuem uma integração entre seus bancos de dados, ou seja, armazenam e consultam apenas os dados locais. Isso é indesejável não somente para informações financeiras e contábeis, mas também no âmbito de gerência de redes. Devido ao crescimento do número de tecnologias de acesso a Internet que usam banda larga e por conseqüência seu barateamento, surge a possibilidade de utilização destes serviços nas empresas. Assim como o crescimento do número de softwares de banco de dados com suporte a distribuição de informações (e seu barateamento) facilita a integração de dados. O emprego de banco de dados distribuídos e gerência de redes de forma conjunta torna as informações de gerência (além de dados diversos das filiais) mais integradas e fáceis de se consultar e analisar

Using semantic values to facilitate interoperability among heterogeneous information systems

Includes bibliographical references (p. 30-32).Supported in part by the NSF. IRI-90-2189 Supported in part by the International Financial Services Research Center at MIT.Michael Siegal [sic], Edward Sciore, Arnon Rosenthal

Evolutionary techniques for updating query cost models in a dynamic multidatabase environment

Deriving local cost models for query optimization in a dynamic multidatabase system (MDBS) is a challenging issue. In this paper, we study how to evolve a query cost model to capture a slowly-changing dynamic MDBS environment so that the cost model is kept up-to-date all the time. Two novel evolutionary techniques, i.e., the shifting method and the block-moving method, are proposed. The former updates a cost model by taking up-to-date information from a new sample query into consideration at each step, while the latter considers a block (batch) of new sample queries at each step. The relevant issues, including derivation of recurrence updating formulas, development of efficient algorithms, analysis and comparison of complexities, and design of an integrated scheme to apply the two methods adaptively, are studied. Our theoretical and experimental results demonstrate that the proposed techniques are quite promising in maintaining accurate cost models efficiently for a slowly changing dynamic MDBS environment. Besides the application to MDBSs, the proposed techniques can also be applied to the automatic maintenance of cost models in self-managing database systems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47868/1/778_2003_Article_110.pd

Bancos de dados distribuídos heterogêneos: arquiteturas, tecnologias e tendências /

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico.Com o desenvolvimento das empresas e instituições, surge a necessidade de integração dos sistemas de bancos de dados preexistentes, autônomos e diferentes. A utilização de Sistemas de Bancos de Dados Heterogêneos, por sua capacidade de integrar arquiteturas diferentes, apresenta-se como uma alternativa interessante para a solução do problema de integração dos dados. A tecnologia de Sistemas de Dados Heterogêneos permite que sistemas de modelos, fabricantes e produtos diferentes possam ser integrados de forma a oferecer uma visão única ao usuário. No entanto, devido à autonomia e heterogeneidade dos sistemas existentes, este ambiente apresenta muitos desafios. Acessar e gerenciar dados originários de vários bancos de dados independentes gera vários problemas. Este trabalho apresenta um estudo e análise sobre os principais problemas e soluções propostas para a integração de bases de dados heterogêneas. Foram analisadas as principais abordagens utilizadas por diferentes autores para tratar problemas relacionados ao processamento/otimização de consultas, gerenciamento/concorrência de transações e interoperabilidade em ambientes autônomos e heterogêneos. Por fim, apresentamos comentários sobre alguns projetos de sistemas gerenciadores de bancos de dados heterogêneos que vem sendo desenvolvidos nos últimos anos

Interface Capabilities for Query Processing in Peer Mediator Systems

A peer mediator system (PMS) is a decentralized mediator system based on the P2P paradigm, where mediators integrate data sources and other mediators through views defined in a multi-mediator query language. In a PMS mediator peers compose views in terms of views in other peers - mediators and sources, or directly pose queries in the multi-mediator query language to some peer. All peers are fully autonomous and there is no central catalog or controller. Each peer in a PMS must provide an interface to its data and meta-data sufficient to allow the cooperative processing of queries by the PMS. We analyze the computational capabilities and meta-data that a software system has to export in order to participate as a peer in a PMS. For the analysis we identify and compare six classes of peer interfaces with increasing complexity. For each class we investigate the performance and scalability implications that result from the available capabilities and required meta-data. Our results are two-fold: i) we provide guidelines for the design of mediator peers that can make best use of the interfaces provided by the data sources, and ii) we analyze the tradeoffs in the design of inter-mediator interfaces so that mediator peers can efficiently cooperate to process queries against other composed mediators. Finally we describe the choices made in a concrete implementation of a PMS