On using genetic algorithms for multimodal relevance optimisation in information retrieval

International audienceThis paper presents a genetic relevance optimisation process performed in an information retrieval system. The process uses genetic techniques for solving multimodal problems (niching) and query reformulation techniques commonly used in information retrieval. The niching technique allows the process to reach different relevance regions of the document space. Query reformulation techniques represent domain knowledge integrated in the genetic operators structure in order to improve the convergence conditions of the algorithm. Experimental analysis performed using a TREC sub-collection validates our approach

Multiple query evaluation based on an enchanced genetic algorithm

International audienceRecent studies suggest that significant improvement in information retrieval performance can be achieved by combining multiple representations of an information need. The paper presents a genetic approach that combines the results from multiple query evaluations. The genetic algorithm aims to optimise the overall relevance estimate by exploring different directions of the document space. We investigate ways to improve the effectiveness of the genetic exploration by combining appropriate techniques and heuristics known in genetic theory or in the IR field. Indeed, the approach uses a niching technique to solve the relevance multimodality problem, a relevance feedback technique to perform genetic transformations on query formulations and evolution heuristics in order to improve the convergence conditions of the genetic process.The effectiveness of the global approach is demonstrated by comparing the retrieval results obtained by both genetic multiple query evaluation and classical single query evaluation performed on a subset of TREC-4 using the Mercure IRS. Moreover, experimental results show the positive effect of the various techniques integrated to our genetic algorithm model

Accès personnalisé à l'information : Vers un modèle basé sur les diagrammes d'influence

National audienceL'accroissement sans précédent des masses d'informations via le Web, lance à la communauté en recherche d'information (RI) de nouveaux défis. En effet, compte tenu des exigences liées à l'efficacité, la personnalisation du processus d'accès à l'information devient incontournable. Son objectif fondamental est de présenter à l'utilisateur des informations pertinentes et intelligibles compte tenu de ses centres d'intérêts, ses préférences, son intention ou plus globalement son profil. Nous présentons dans cet article, les bases de construction d'un modèle d'accès à l'information basé sur les diagrammes d'influence, et mettant en jeu trois composantes : le document, la requête et l'utilisateur. Ce modèle vise à mettre l'utilisateur, décrit par ses centres d'intérêt, au centre du processus de sélection de l'informatio

Tailored Protocol Development Using ESTEREL

The rapid evolution of networking and the multiplication of new applications re-emphasizes the importance of the efficient communication supports. Implementations must be able to take maximal advantage of the details of application-specific semantics and of specific networking environments. In other words, the application needs to have more control over data transmission. Such control can be obtained by tailoring the communication facilities (or protocols) to the application characteritics, and by integrating the communication control to the application. Because such a task is too complex to be realized manually, we propose to automate the protocol development process using a formal approach. This report presents our approach to the automated design and implementation of application- specific communication protocols based on information provided by the application. Starting from the formal description of an application, our approach is based on a tool called "Protocol Compiler" that will automatically produce the implementation of a communication protocol tailored to the application. The formalism we use is ESTEREL, a synchronous reactive language dedicated to the description of real-time systems. Protocol description and verification using ESTEREL are described, as well as protocol optimization and implementation principles

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Document multimédia: indexation et recherche

International audienc

Document multimédia: indexation et recherche

International audienc

Bases de Documents multimedia

Pages de la publication : ..International audienc

Annotations de média : Vers une représentation multidimensionnelle

International audienc