PhD graduated
Team : ComplexNetworks
Departure date : 12/09/2016

Supervision : Matthieu LATAPY

Co-supervision : MAGNIEN Clémence

Groups and Communities in link streams: from data to algorithms

Interactions are everywhere: in the contexts of face-to-face contacts, emails, phone calls, IP traffic, etc. In all of them, an interaction is characterized by two entities and a time interval: for instance, two individuals meet from 1pm to 3pm.
We model them as link stream which is a set of quadruplets (b,e,u,v) where each quadruplet means that a link exists between u and v from time b to time e. In graphs, a community is a subset which is more densely connected than a reference. Within the link stream formalism, the notion of density and reference have to be redefined. Therefore, we study how to extend the notion of density for link streams. To this end, we use a real data set where a community structure is known. Then, we develop a method that finds automatically substream which are considered relevant. These substream, defined as subsets of links, are discovered by a classical community detection algorithm applied on the link stream then transformed into a static graph. A substream is considered relevant, if it is denser than the substreams which are close temporally and structurally. Thus, we deepen the notion of neighbourhood and reference in link streams.
We apply our method on several real world interaction networks and we find relevant substream which would not have been found by existing methods. Finally, we discuss the generation of link streams having a given community structure and also a proper way to evaluate such community structure.

Defence : 10/11/2016 - 10h - Site Jussieu 25-26/105

Jury members :

David Chavalarias, CR CNRS, CAMS-EHESS [Rapporteur]
Jean-Loup Guillaume, Professeur des Universités, L3I (La rochelle) [Rapporteur]
Bertrand Jouve, DR CNRS, FRAMESPA
Catherine Mathias, DR CNRS, PMA
Véronique Serfaty, Docteur, responsable scientifique DGA-MRIS
Gilles Tredan, CR CNRS, LAAS
Clémence Magnien, DR CNRS, LIP6
Matthieu Latapy, DR CNRS, LIP6

2014-2018 Publications