1. Institute of Information Systems, Universitiy of Applied Sciences and Arts Western Switzerland (HES-SO Valais-Wallis), Switzerland. E-mails: jean-paul.calbimonte@hevs.ch, fabien.dubosson@hevs.ch
2. Distributed Information Systems Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland. E-mails: jean-eudes.ranvier@epfl.ch, karl.aberer@epfl.ch