1. a Keyplatform Company , 75008 Paris, France
2. b Laboratory of Industrial Engineering, Ecole Centrale Paris , Chatenay-Malabry, France
3. c IRCCyN, Ecole des Mines de Nantes, CNRS UMR 6597 , F-44300 Nantes, France
4. d Laboratoire Informatique d’Avignon , 84911 Avignon Cedex 9, France