1. INRIA, Lille France
2. Mines Saint‐Etienne Univ Clermont Auvergne CNRS UMR 6158 LIMOS, Institut Henri Fayol Saint‐Etienne F ‐ 42023 France
3. Mines Saint‐Etienne Univ Clermont Auvergne CNRS UMR 6158 LIMOS, Centre CIS Saint‐Etienne F ‐ 42023 France