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Conference Papers Year : 2012

The WebdamLog System: Managing Distributed Knowledge on the Web


The focus of this paper is on the management of distributed knowledge, in environments where a large number of autonomous and heterogeneous systems collaborate to support cer- tain tasks. All information is represented as logical facts, and tasks correspond to logical rules. We use the language WebdamLog, a recently introduced variant of datalog for dis- tributed data management. The main novelty of WebdamLog compared to datalog is its use of delegation, that is, the ability for a peer to communicate a program to another peer. This paper introduces a WebdamLog inference engine. Our main contribution is to demon- strate that such an engine may be implemented with good performance for very dynamic applications, i.e., for applications with rapidly evolving knowledge and with heavy knowledge exchange. To avoid reimplementing standard features of datalog engines, we developed Web- damLog on top of the Bud system, which has already been demonstrated to be very efficient. In this paper, we describe our implementation of the features that are specific to WebdamLog, and include: (1) support for complex rules with predicates in the rule body that are evaluated by remote peers; (2) support for variables for peer and predicate names that allow for very flexible management of distribution, e.g., for the discovery of new peers; and (3) management of delegations that lead to changes in the programs of remote peers. Our focus on dynamic peer state and on rapidly evolving knowledge leads to new perfor- mance challenges, prompting us to introduce new evaluation techniques. A key component of our approach is a novel kind of a provenance graph that allows for performance optimiza- tions in this dynamic context. We describe the provenance graph and its use for performance optimizations, and outline experiments that we are conducting.
Ce papier traite de la gestion des bases de connaissances distribuées, dans des environne- ments où un grand nombres de pairs autonomes et hétérogènes collaborent pour réaliser des tâches. Les informations sont représentées par des faits et les tâches correspondent à des règles logiques. Nous utilisons le langage WebdamLog, une variante de datalog pour les données dis- tribuées. Nous présentons l'implémentation d'un moteur WebdamLog et nous montrons son efficacité dans le cadre d'applications distribuées dans lesquels les pairs changent rapidement leurs bases de connaissances. Notre implémentation s'appuie sur Bud pour l'évaluation stan- dard de datalog. Le moteur WebdamLog étends Bud avec le support (1) de règles avec des prédicats non locaux dans le corps ; (2) de règles avec des variables pour les prédicats ou les noms des pairs ; (3) la gestion des délégations qui changent le programme des pairs distants.
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hal-00805797 , version 1 (04-04-2013)


  • HAL Id : hal-00805797 , version 1


Serge Abiteboul, Émilien Antoine, Julia Stoyanovich. The WebdamLog System: Managing Distributed Knowledge on the Web. Base de données avancées, Oct 2012, Clermont-Ferrand, France. ⟨hal-00805797⟩
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