1. LORIA, Université de Lorraine, CNRS, INRIA 54506, Vandœuvre-lès-Nancy, France
2. Fraunhofer FOKUS, 10589 Berlin, Germany
3. Weizenbaum Institute for the Networked Society, 10623 Berlin, Germany
4. LaSIGE, Faculdade de Ciêcias, Universidade de Lisboa, 1749-016 Lisboa, Portugal