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

Comparing paedophile activity in different P2P systems

Peer-to-peer (P2P) systems are widely used to exchange content over the Internet. Knowledge on paedophile activity in such networks remains limited while it has important social consequences. Moreover, though there are different P2P systems in use, previous academic works on this topic focused on one system at a time and their results are not directly comparable. We design a methodology for comparing \kad and \edonkey, two P2P systems among the most prominent ones and with different anonymity levels. We monitor two \edonkey servers and the \kad network during several days and record hundreds of thousands of keyword-based queries. We detect paedophile-related queries with a previously validated tool and we propose, for the first time, a large-scale comparison of paedophile activity in two different P2P systems. We conclude that there are significantly fewer paedophile queries in \kad than in \edonkey (approximately 0.09% \vs 0.25%).Comment: Submitte

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

Transport of video over partial order connections

A Partial Order and partial reliable Connection (POC) is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. Such a connection is also authorized to lose some objects. The POC concept is motivated by the fact that heterogeneous best-effort networks such as Internet are plagued by unordered delivery of packets and losses, which tax the performances of current applications and protocols. It has been shown, in several research works, that out of order delivery is able to alleviate (with respect to CO service) the use of end systems’ communication resources. In this paper, the efficiency of out-of-sequence delivery on MPEG video streams processing is studied. Firstly, the transport constraints (in terms of order and reliability) that can be relaxed by MPEG video decoders, for improving video transport, are detailed. Then, we analyze the performance gain induced by this approach in terms of blocking times and recovered errors. We demonstrate that POC connections fill not only the conceptual gap between TCP and UDP but also provide real performance improvements for the transport of multimedia streams such MPEG video

IP Multicast Security

Support de cours.With emerging of new cooperative applications, the group communication is clearly become a very important concept within the network architecture. The multicast transmission is appeared as the most efficient way to send some data to a specific group composed of several participants like used in multimedia applications (audio and video conferences, video diffusion,...) But today, we can see that commercial multicast deployment is not a reality yet. This model presents some limits such as: scalable routing problems, address allocation problems and mainly security issues because any host can send data to IP multicast address and any host can join Nowadays the increasing interest in network communication through the using of the Internet requires some services such as authentication, integrity and confidentiality to transport securely data. The lack of security in multicast communications is essentially due to the difficulty to develop solutions which are efficient and fault tolerant. In our tutorial, we present : * Security issues within group communications and why the approaches to secure the unicast communications cannot be directly applied to group communications. * Research work related to key management and key distribution. * Research work related to source authentication. * Fault tolerance within group communications

Fighting against paedophile activities in the KAD P2P network

International audienceIn this short paper, we present a solution to fight against paedophile activities in KAD. Our distributed architecture can monitor and act on paedophile contents in a very efficient way by controlling keywords and files. Early results on the real network demonstrate the applicability of our approach

Green Growth in NDN: Deployment of Content Stores

International audienceNamed-Data Networking architecture relies on cache networks, where nodes store the data for further requests. However, the memory needed at each node called Content Store represents the most significant part of the entire cost of the infrastructure that has to be supported by network providers, making difficult the change from the current Internet infrastructure to a Future Internet based on NDN. Thus, a legitimate question would be: "are all these Content Stores useful in a large-scale NDN network?" In this paper, we investigate theimpact of Content Stores in NDN network, and we evaluate the performances of the NDN architecture according to the number of Content Stores effectively deployed in the network. We show through extensive simulation experiments in NS-3 that only about 50% of nodes with Content Stores is enough to achieve higher level of performances than a fully-deployed NDN network. This result is very important for the deployment of NDN architecture as it shows that the infrastructure cost can be drastically reduced and it is an incentive for network providers that benefits directly from this result