Optimizing Repetitive Computations of Database Triggers Within a Transaction

Projet RODINWe study the problem of optimizing costly repetitive evaluations of database triggers within a transaction. We first show that well known incremental rule evaluation algorithms such as RETE or TREAT are inappropriate for that because they do not consider how repetitive triggerings of rules can be caused by the structure of transaction programs. Therefore, their decision of precomputing and caching some expressions in rule conditions for a later reuse can be erroneous. We assume that transaction programs are represented by their flow graph. We then propose an algorithm that, given a transaction's flow graph, and a set of triggers, constructs a compact data structure called a triggering graph. First, for each possible transaction execution, this graph indicates which rules may be triggered. Second, for every rule $r$ capable of being triggered and fired several times, the graph represents the real «influence» of both the transaction and the rules on $r$. This provides the necessary information for deciding which subexpressions of $r$ are most profitable to cache for the considered transaction

Bancos de dados ativos como suporte a restrições topologicas em sistemas de informação geografica

Claudia Maria Bauzer MedeirosDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Ciencia da ComputaçãoResumo: Esta dissertação trata da utilização de sistemas ativos no contexto de aplicações geográficas. Os resultados aqui apresentados estendem o paradigma de SGBD ativos com o objetivo de solucionar o problema de manutenção de relacionamentos espaciais (topológicos) na presença de atualizações. A solução apresentada para este problema está dividida em três etapas: i) especificação da restrição topo lógica; ii) transformação da restrição em regras; e iii) manutenção automática da restrição, com base nas regras geradas. Esta abordagem foi utilizada no desenvolvimento de um protótipo de sistema ativo que incorpora um modelo geográfico OO, eliminando o problema da impedância existente entre Sistemas de Informação Geográfica (SIG) e sistemas de regras. As principais contribuições deste trabalho são um estudo detalhado sobre relacionamentos topológicos binários; uma proposta integrada para o problema de manutenção desses relacionamentos; e a definição de algoritmos para a verificação de integridade topológica, implementados no protótipo.Abstract: This dissertation concerns the use of active databases in geographic applications. The results presented here extend the active database systems paradigm to solve the problem of maintaining spatial (topological) constraints. The solution for this problem is divided in three steps: i) topological constraint specification; ii) translation of the constraint into roles; and iii) automatic constraint maintenance, using the generated rules. This approach was used in the development of an active system prototype that incorporates an object-oriented geographic model, thus removing the gap between Geographic Information Systems (GIS) and role systems. The main contributions presented are a detailed study about binary topological relationships; an integrated proposal for the problem of maintaining these relationships; and the definition of algorithms to verify the topological integrity (these algorithms are incorporated in the prototype).MestradoMestre em Ciência da Computaçã

Implementing Integrity Control In Active Data Bases

This article presents a system for maintaining static integrity constraints in data bases that uses the active data base paradigm. This system has been added to an active version of the O2 object-oriented data base system, and it is fully functional. Constraints, specified by the user in a fist-order logic language, are transformed into production rules, which are stored in the data base. These rules are used to maintain the corresponding set of constraints for all applications that use the data base. We extend previous work on constraint maintenance in two ways: our system can be used as a constraint maintenance layer on top of object-oriented, relational, and nested relational data bases, and for object-oriented systems, we provide constraint support not only in the case of object composition, but also consider inheritance and methods. © 1994.273171181Adiba, Collet, Coupaye, Habraken, Machado, Martin, Roncancio, Trigger Systems: Different Approaches (1993) Technical Report Aristote-SUR007, , Laboratoire de Génie Informatique, IMAG, Grenoble, FranceAndrade, Manutenção de Restrições de Integridade em Bancos de Dados Orientados a Objetos (1992) Master's Thesis, , Department of Computer Science, UNICAMP, CampinasAiken, Widom, Hellerstein, Behavior of Database Production Rules: Termination, Confluence and Observable Determinism (1992) Technical Report FJ8562, , IBM, AlmadenBuchmann, Branding, Kudrass, Zimmermann, REACH—A REal-Time, ACtive and Heterogeneous Mediator System (1992) IEEE Bull. 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