Actes de la conférence BDA 2014 : Gestion de données - principes, technologies et applications

International audienceActes de la conférence BDA 2014 Conférence soutenue par l'Université Joseph Fourier, Grenoble INP, le CNRS et le laboratoire LIG. Site de la conférence : http://bda2014.imag.fr Actes en ligne : https://hal.inria.fr/BDA201

Performances de protocoles transactionnels en environnement mobile

National audience. L'omniprésence d'unités mobiles et le développement des réseaux sans fil motivent des avancées en matière de supports d'exécution pour une grande variété d'applications en envi-ronnement mobile. Des efforts importants sont faits pour offrir une bonne gestion des données malgré les caractéristiques limitées de tels environnements. La notion de transaction a été ré-étudiée pour proposer des modèles et des protocoles permettant d'assurer certaines propriétés transactionnelles. Les algorithmes et protocoles proposés tentent d'optimiser l'utilisation des ressources des unités mobiles et de surmonter les limitations du réseau mobile. Dans cet article nous nous intéressons spécifiquement aux protocoles de validation de transactions réparties sur plusieurs unités dont certaines mobiles. Nous présentons ici les résultats d'un travail qui iden-tifie des propriétés qualitatives et des indices de performance quantitatifs, et étudie ceux-ci sur quatre protocoles (2PC, UCM, CO2PC et TCOT). Trois de ces protocoles sont des propositions spécifiques pour des environnements mobiles et sont représentatifs des propositions actuelles. Nous nous intéressons à la phase de validation des transactions, ainsi qu'à l'influence des dif-férents protocoles sur les performances du déroulement de l'ensemble des transactions. ABSTRACT. This is an abstract. The omnipresence of mobile devices and wireless networks lead to a growing interest in supporting a wide variety of applications in mobile environments. Numerous efforts in providing appropriate data managements for such environments are made. Transaction supports have been revisited to propose adapted transaction models and properties. Proposed algorithms and protocols try to optimise the use of mobile units resources and to overcome wireless network limitations. This work concerns protocols to commit transactions distributed over several mobile and fixed units. Results presented here concern the identification of qualitative properties and quantitative performance indices that are studied on four protocols (2PC, UCM, CO2PC et TCOT). Three of them are specifics propositions for mobile environments and are representative of current proposals. The analysis concerns the transaction validation phase as well as the impact of the protocols on the performances during a transaction execution itself. MOTS-CLÉS : transactions mobiles , evaluation de performances, protocoles de validation

E-Commerce : Stratégies et Pratiques

Engineering schoolCe cours présente les stratégies de l'E-Commerce et leur mise en pratique sur Apache-PHP avec le CMS Wordpress

A unilateral commit protocol for mobile and disconnected computing

Databases are hosted by a growing number of lightweight intelligent devices like palmtops, cellular phones, car computers and even smart cards. Mobility and disconnected computing are two major issues in such environment. This paper deals with the way databases can be exploited in this context while maintaining a strong transactional coherency. More precisely, we argue that 2PC, the most well known and well-established atomic commitment protocol, is far from being adapted to this environment. We propose a new atomic commitment protocol, called Unilateral Commit for Mobile (UCM), that exhibits the following properties: it supports off-line executions and disconnection during commitment, it decreases the cost of wireless communication by reducing the message complexity and it saves resources on lightweight servers. These properties are obtained at the price of some assumptions on the way servers manage transactions. Anyway, we show that these assumptions are not constraining in the considered environment

Using case base reasoning for database query optimization in ubiquitous environments

National audienceClassic query optimization techniques use metadata (e. g. statistics) to estimate the cost of di erent possible solutions (query plans) to evaluate a query and choose the one that minimizes a cost function. This cost function determines the optimization objective, which is generally the evaluation time. In ubiquitous computing environments, where devices are autonomous and have limited physical characteristics (e.g. energy or CPU power), the evaluation time of queries is no longer the main optimization objective. Moreover metadata required for a priori estimating the evaluation cost of query plans are not always available. In order to solve this problem, this article describes a new query optimization technique based on automatic learning, particularly on case-based reasoning. This technique is not another cost function-based query optimization technique. It considers a query case base where cases represent experiences of queries that have been previously executed, optimized and evaluated. It address the exploitation of the case base for generating execution plans and learning on existing ones according to measures inserted in the case base. Currently we are working in the prototype that implements the query optimization techique that we propose

DWS: a data placement approach for Smart Grid Ecosystems

International audienc

Compatibility Checking Between Privacy and Utility Policies: A Query-Based Approach

Data sharing over the internet through smart devices is susceptible to disclose sensitive information of data producers. To protect the privacy of data producers, we propose a querybased approach where data producers keep their data on decentralized personal data servers and only disclose data to data consumers over secure communication links according to their privacy policies. Data consumers specify the data needed to provide services as utility policies. In our approach, we express the privacy and utility policies as sets of temporal aggregated conjunctive queries. We make explicit several sufficient conditions of compatibility between privacy and utility policies based on their query expressions. On the basis of these results, sensitive data breaches can be prevented by checking whether one of these sufficient conditions is satisfied

Explanation-based Tool for Helping Data Producers to Reduce Privacy Risks

This paper demonstrates the interactive user interface P rivEx that helps data producers to reduce privacy risks raised by data collection from service providers in the Semantic Web of Things. P rivEx provides several types of support to data producers in their management of the tension between the privacy risks and the utility of the data they accept to publish. P rivEx is grounded on the formal framework presented in [1] for detecting automatically privacy risks raised by utility queries. In the demonstration, we will illustrate the functionalities of P rivEx, on a smart meter scenario inspired by a real-world use case providing time series of electrical consumptions of different customers associated with some metadata on their demographics, home sizes and equipment

Identifying Privacy Risks raised by Utility Queries

International audiencePersonal data are increasingly disseminated over the Web through mobile devices and smart environments, and are exploited for developing more and more sophisticated services and applications. All these advances come with serious risks for privacy breaches that may reveal private information wanted to remain undisclosed by data producers. It is therefore of utmost importance to help them to identify privacy risks raised by requests of service providers for utility purposes. In this paper, we first formalize privacy risks by privacy queries expressed (and kept secret) by each data producer to specify the data they do not want to be disclosed. Then, we develop a formal approach for detecting incompatibility between privacy and utility queries expressed as temporal aggregate conjunctive queries. The distinguishing point of our approach is to be data-independent and to come with an explanation based on the query expressions only. This explanation is intended to help data producers understand the detected privacy breaches and guide their choice of the appropriate technique to correct it

The QOL approach for optimizing distributed queries without complete knowledge

Session: QoS, Query Processing, Optimization (full paper)International audienceThis paper concerns the integration of the Case Based Reasoning (CBR) paradigm in query processing, providing a way to optimize queries when there is no prior knowledge on queried data sources and certainly no related metadata such as data statistics. Our Query Optimization by Learning (QOL) approach optimizes queries using cases generated from the evaluation of similar past queries. A query case comprises: (i) the query, (ii) the query plan and (iii) the measures (computational resources consumed) of the query plan. The work also concerns the way the CBR process interacts with the query plan generation process. This process uses classical heuristics and makes decisions randomly (e.g. when there is no statistics for join ordering and selection of algorithms, routing protocols); It also (re)uses cases (existing query plans) for similar queries parts, improving the query optimization and evaluation efficiency