![]() Our experimental results show the accuracy of cost calculus when using GSD, and the flexibility of our generic framework when changing search strategies. Our generic framework for query optimization provides a set of unitary functions used to perform optimization by applying different search strategies. With GSD, we can use cost information to calculate the costs of execution plans. We propose a generic source description model (GSD), which allows describing any type of information related to query processing and optimization. This thesis proposes a generic framework for query optimization in heterogeneous and distributed environments. It is a running research vehicle designed at PRiSM Laboratory for assessing the integration system at every stage of the process starting from sources extraction to the user interf ace and is already used in several projects. XLive integrates sources in a uniform view. Our paper is based on the XLive mediation system. Models based on Tree Patterns have been proposed, and we have extended the tree pattern model to a model called TGV that (a) integrates the whole functionalities of XQuery (b) uses an intuitive representation that provides a global visualization of the request in a mediatio n context and (c) provides a support for optimization and for cost information. The XQuery expressiveness makes difficulties to obtain an ex clusive internal representation within a system. We have extended (Chen et al., 2003) proposal to rewrite XQuery expressions in "canonical XQuery" in order to support the full XQuery specification. Its syntax allows us to express a large scale of queries over XML documents. ![]() XQuery(W3C, 2005) is a rich and so a complex language. This paper presents an efficient evaluation of XQuery in a het erogeneous distributed system. ![]()
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