Egomunities, Exploring Socially Cohesive Person-based Communities

In the last few years, there has been a great interest in detecting overlapping communities in complex networks, which is understood as dense groups of nodes featuring a low outbound density. To date, most methods used to compute such communities stem from the field of disjoint community detection by either extending the concept of modularity to an overlapping context or by attempting to decompose the whole set of nodes into several possibly overlapping subsets. In this report we take an orthogonal approach by introducing a metric, the cohesion, rooted in sociological considerations. The cohesion quantifies the community-ness of one given set of nodes, based on the notions of triangles - triplets of connected nodes - and weak ties, instead of the classical view using only edge density. A set of nodes has a high cohesion if it features a high density of triangles and intersects few triangles with the rest of the network. As such, we introduce a numerical characterization of communities: sets of nodes featuring a high cohesion. We then present a new approach to the problem of overlapping communities by introducing the concept of ego-munities, which are subjective communities centered around a given node, specifically inside its neighborhood. We build upon the cohesion to construct a heuristic algorithm which outputs a node's ego-munities by attempting to maximize their cohesion. We illustrate the pertinence of our method with a detailed description of one person's ego-munities among Facebook friends. We finally conclude by describing promising applications of ego-munities such as information inference and interest recommendations, and present a possible extension to cohesion in the case of weighted networks

Internet comme vecteur de pouvoir

Cet article propose une étude des modalités de fonctionnement du bloc historique contemporain à partir du cas de la gouvernance d’Internet. L’analyse est fondée sur le cadre théorique multidisciplinaire inspiré de la théorie critique du droit et adopte une perspective néogramscienne afin de circonscrire l’exercice d’un pouvoir que les approches statocentrées décrivent inadéquatement. Il est plus particulièrement question du pouvoir que peut procurer le contrôle normatif du système communicationnel et de l’instrumentalisation du droit permettant de reproduire un statu quo favorable aux acteurs dominants du système international. L’auteur démontre ainsi que l’Internet peut non seulement renforcer le pouvoir des classes dominantes, mais également servir d’outils à des contre-pouvoirs potentiels.This paper offers an analysis of the modus operandi of the contemporary historical block while focusing on the issue of Internet governance. It develops a multidisciplinary theoretical framework inspired by the Critical Legal Theory and the Neo-gramscian perspective in order to show the significance of such a diffuse form of power which state-centered perspectives hide the subtlety of. It sheds light on the power that can be obtained from the regulatory control of communication systems, and of the instrumentalization of law in reproducing the social status quo favorable to dominant actors within the international system. It however argues that Internet not only reinforces the power of the dominant classes but also potentially empowers counter-hegemonic social forces

Triangles to Capture Social Cohesion

Although community detection has drawn tremendous amount of attention across the sciences in the past decades, no formal consensus has been reached on the very nature of what qualifies a community as such. In this article we take an orthogonal approach by introducing a novel point of view to the problem of overlapping communities. Instead of quantifying the quality of a set of communities, we choose to focus on the intrinsic community-ness of one given set of nodes. To do so, we propose a general metric on graphs, the cohesion, based on counting triangles and inspired by well established sociological considerations. The model has been validated through a large-scale online experiment called Fellows in which users were able to compute their social groups on Face- book and rate the quality of the obtained groups. By observing those ratings in relation to the cohesion we assess that the cohesion is a strong indicator of users subjective perception of the community-ness of a set of people

Worldsens: development and prototyping tools for application specific wireless sensors networks

International audienceIn this paper we present Worldsens, an integrated environment for development and rapid prototyping of wireless sensor network applications. Our environment relies on software simulation to help the designer during the whole development process. The refinement is done starting from the high level design choices down to the target code implementation, debug and performance analysis. In the early stages of the design, high level parameters, like for example the node sleep and activity periods, can be tuned using WS-Net, an event driven wireless network simulator. WSNet uses models for applications, protocols and radio medium communication with a parameterized accuracy. The second step of the sensor network application design takes place after the hardware implementation choices. This second step relies on the WSim cycle accurate hardware platform simulator. WSim is used to debug the application using the real target binary code. Precise performance evaluation, including real-time analysis at the interrupt level, are made possible at this low simulation level. WSim can be connected to WSNet, in place of the application and protocol models used during the high level simulation to achieve a full distributed application simulation. WSNet and WSNet+WSim allow a continuous refinement from high level estimations down to low level real-time validation. We illustrate the complete application design process using a real life demonstrator that implements a hello protocol for dynamic neighborhood discovery in a wireless sensor network environment

Communautés : Arrêtons de ne compter que les arêtes

International audienceDans cet article, nous souhaitons revenir sur la question de la définition d'une communauté en tant qu'ensemble de sommets U sans avoir à en juger la qualité au regard des autres communautés, recouvrantes ou non. Ce qui importe c'est uniquement l'ensemble U considéré et le graphe sous-jacent et ce indépendamment de tout découpage global. À dessein, nous introduisons la " cohésion " qui repose sur la relation forte qui existe entre des triplets de sommets lorsqu'ils forment un triangle ou au contraire sur la non présence de triangle traduisant la présence de lien faible (notion de "weak tie" introduite par A. Rapoport en 1957 et reprise par M.S. Granovetter en 1973). La notion de communauté découle de cette mesure confinée à un sous-ensemble de sommets plongé dans son graphe d'origine : une communauté est un ensemble de sommets offrant une forte cohésion. Après avoir introduit la métrique de cohésion, nous illustrons son application sur la découverte de communautés egocentrées dans des réseaux sociaux en utilisant un algorithme se basant sur la cohésion et donnons quelques résultats sur l'application de ce calcul d'egomunautés

Energy aware unicast geographic routing

Abstract — In this paper, we are investigating the optimal radio range minimizing the energy globally consummed by a geographical routing process. Considering a geographical greedy routing protocol and a uniform distribution of nodes in the network area, we analytically evaluate the energy cost of a multi-hop communication. This cost evaluation corresponds to the asymptotic behavior of the routing protocol and turns out to be very accurate compared to the results obtained by simulations. We show that this cost is function of the node intensity and we use this result to deduce the optimal radio range. We evaluate this range with two energy consumption models, the first one considering the energy consumed by transmission operations only and the second one considering both transmission and reception operations. These results can be used in two ways. First, the nodes range can be tuned in advance as a function of the expected node intensity during an off-line planning. Second, we propose an adaptative algorithm where nodes tune their powers according to an on-line evaluation of the local node intensity. I

Demonstration of worldsens: a fast prototyping and performance evaluation of wireless sensor network applications & protocols

International audienceWe present Worldsens, a complete environment for fast prototyping of wireless sensor protocols and applications. Our environment proposes a full simulation platform with both embedded software instruction and radio packet accuracy. We propose a demonstration including a full software design, simulation, performance estimation and deployment on a set of nodes within the same design environment. Through these first experimentations, we show that accurate sensor network simulation is feasible and that complex application design and deployment is affordable

Un illusoire consensus ? La densité politique de la Coupe du monde de football en Amérique latine

L’année 2014 a été chargée au plan politique et sportif en Amérique latine. Parmi les neuf pays de la région qualifiés pour la Coupe du monde masculine de football, qui s’est déroulée du 12 juin au 13 juillet 2014 au Brésil, quatre ont tenu la même année des élections générales : le Costa Rica (février), la Colombie (mai-juin), le Brésil (octobre) et l’Uruguay (octobre). La convergence des calendriers a été particulièrement marquante en Colombie, où le second tour de l’élection présidentielle s’est joué le 15 juin, le lendemain de la victoire de la sélection nationale contre la Grèce. Si aucune étude d’analyse électorale n’a pu, à notre connaissance, prouver une corrélation réelle entre les résultats des équipes nationales de football et les comportements électoraux (vote-sanction en cas de défaite ou vote de reconnaissance en cas de succès), les enjeux politiques du football n’en sont pas moins importants et repérables à différents niveaux. Ils se manifestent avec une vigueur et une visibilité accrues à l’approche d’un événement aussi populaire et médiatisé qu’une Coupe du monde..