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Smartcards are the most secure portable computing device today. They have been used successfully in applications involving money, proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with 32 bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for(More)
Discovery of association rules is an important problem in Data Mining. The classical approach is to generate all itemsets that have support (i.e., the fraction of transactions containing the itemset) above a user given threshold. Most existing algorithms aim at reducing the number of scans over the transaction database, i.e., the I/O overhead. We consider(More)
NAND Flash has become the most popular stable storage medium for embedded systems. As on-board storage capacity increases, the need for efficient indexing techniques arises. Such techniques are very challenging to design due to a combination of NAND Flash constraints (for example the block-erase-before-page-rewrite constraint and limited number of erase(More)
The erosion of trust put in traditional database servers and in Database Service Providers, the growing interest for different forms of data dissemination and the concern for protecting children from suspicious Internet content are different factors that lead to move the access control from servers to clients. Several encryption schemes can be used to serve(More)
With the emergence of XML as the de facto standard to exchange and disseminate information, the problem of regulating access to XML documents has attracted a considerable attention in recent years. Existing models attach authorizations to nodes of an XML document but disregard relationships between them. However, ancestor and sibling relationships may(More)
Pervasive computing introduces data management requirements that must be tackled in a growing variety of lightweight computing devices. Personal folders on chip, networks of sensors and data hosted by autonomous mobile computers are different illustrations of the need for evaluating queries confined in hardware constrained computing devices. RAM is the most(More)
An increasing amount of personal data is automatically gathered and stored on servers by administrations, hospitals, insurance companies, etc. Citizen themselves often count on internet companies to store their data and make them reliable and highly available through the internet. However, these benefits must be weighed against privacy risks incurred by(More)
The requirements for a main memory data storage model are both compactness and efficient processing for all database operations. The DBGraph storage model, proposed in this paper, achieves these goals. By representing the entire database in a unique graph-based data structure, called DBGraph, it fully exploits the direct-access capability of main memory(More)
1 Although widely used in distributed transactional systems, the so-called Two-Phase Commit (2PC) protocol introduces a substantial delay in transaction processing, even in the absence of failures. This has led several researchers to look for alternative commit protocols that minimize the time cost associated with coordination messages and forced log writes(More)