. These added access control checks can considerably increase query evaluation time. In this paper, we consider the problem of optimizing the secure evaluation of XML twig queries.

This paper introduces a discriminative model for the retrieval of images from text queries. Our approach formalizes the retrieval task as a ranking problem, and introduces a learning procedure optimizing a criterion related to the ranking performance. The proposed model hence addresses

Abstract—We present a new approach to optimization of query languages using cached results of previously evaluated queries. It is based on the stack-based approach (SBA) which assumes descriptionofsemanticsintheformofabstractimplementationof query/programming language constructs. Pragmatic

Abstract. Estimating the sizes of query results, and intermediate results, is crucial to many aspects of query processing. In particular, it is necessary for effective query optimization. Even at the user level, predictions of the total result size can be valuable in “next-step ” decisions

pre- and postprocessing functions can be distinguished from an ideal one with an attack complexity of about 2n/2. Next, we introduce the tweakable blockcipher F ̃ [1]. It consists of one multiplication and one blockcipher call with tweak-dependent key, and achieves 22n/3 security. Finally, we

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;quot;q2, where q is thenumber of MACs the adversary can request. As " is at least 2-k, the best one can hope for is O(q2/2k) security. Unfortunately, such small " is not achieved by simple constructions used inpractice, such as the polynomial evaluation or the Merkle

targets to provide efficient data management optimizations as services. In this paper, we introduce the design and implementation of one such service, the parallel querying service. To answer the queries efficiently, we transparently augment user data with bitmap indexes and ordered datasets. We design

Hiermit versichere ich, die vorliegende Diplomarbeit selbstständig und unter ausschliesslicher Verwendung der angegebenen Quellen und Hilfsmittel angefertigt zu haben. Diese Arbeit hat in gleicher oder ähnlicher Form noch keiner Prüfungsbehörde vorgelegen. Darmstadt, 14. Februar 2006

Hypertree width [22, 25] is a measure of the degree of cyclicity of hypergraphs. A number of relevant problems from different areas, e.g., the evaluation of conjunctive queries in database theory or the constraint satisfaction in AI, are tractable when their underlying hypergraphs have bounded