DIGITEO seminar: lecture on October 20 20 October 2011 Degeneracy Based Community Evaluation Michalis Vazirgiannis, Digiteo chair Supélec, amphi F3.05, 14h30
Abstract -------------- Graphs constitute the dominant data structure in the WWW, and appear essentially in all forms of information. Examples are the web graph, social networks, protein interaction networks, terms dependency graphs etc. Important knowledge is hidden in the macroscopic topology and features of these graphs. The dominant knowledge artifacts extracted from graphs are either individual node based scores (such as authority/hubness/centrality) or unsupervised grouping of nodes in to clusters or global statistics computations (such as degree distributions etc). What is missing is metrics, structures and measures that represent the deeper knowledge hidden in the macroscopic structure of potentially directed/weighted graphs. We propose new metrics and evaluation schemes for the macroscopic structure of graphs capitalizing on the degeneracy concept, i.e. k-cores, towards identifying the most cohesive components of graphs – finding thus the most collaborative constituents. These metrics compute the most robust subgraphs representing dense and mutual connectivity in the case of directed and weighted graphs as well. Connectivity can be then interpreted in several ways: i.e. as collaboration in citation or social networking graphs, collective affinity in protein interaction graphs etc. We also use the best k-cores of graphs as seeds for optimizing the speed of spectral graph clustering. We conducted several experiments on real (DBLP, Wikipedia) and synthetic data sets. The results are interesting especially in the case in the DBLP citation graph.  We further extend k-core to deal with directed graphs, introducing  the D-core concept,  as means of evaluating  a digraph’s collaborative nature. Based on the D-core we devise a  wealth of novel metrics used to evaluate the graphs collaboration features.  We applied the above approaches on large real world graphs - Wikipedia and DBLP -  and report interesting results.  A relevant prototype demo is available at: http://www.lix.polytechnique.fr/~giatsidis/cores/ Pour en savoir plus: http://www.digiteo.fr/Digiteo_NewsSeminaire_Michalis

Yannis Manoussakis passed away
6 June 2021
We have just learned of the death of Yannis Manoussakis, Professor at the University of Paris-Saclay, on Saturday June 5.

He was the leader of the GALaC team and had been for many years director of the LRI, we lose a friend and a dear colleague.

Our

Semaine du cerveau : Cerveau connecté
16 March 2021

Wizard project
1 April 2021
Innovation Area: Public Safety, IoT, Mobility