Chapter 3 Modelling Preferences Denis Bouyssou, Thierry Marchant, Marc Pirlot, Alexis Tsoukiàs, and Philippe Vincke Abstract This chapter deals with a crucial step in the decision aiding process: the aggregation of the alternatives’ performances on each criterion in order to faithfully model the overall preference of the decision maker. The approach we follow is that of conjoint measurement, which aims at determining under which conditions a preference can be represented in a particular aggregation model. This approach is first illustrated with the classical additive value function model. Then, we describe two broad families of preference models, which constitute a framework encompassing many aggregation models used in practice. The aggregation rules that fit with the second family of models rely on the aggregation of preference differences. Among this family we find, in particular, models for the outranking relations (concordance relations with vetoes) that are used in several case studies in this book. D. Bouyssou • A. Tsoukiàs CNRS-LAMSADE UMR 7243, Université Paris Dauphine, Place du Maréchal de Lattre de Tassigny, 75775 Paris Cedex 16, France e-mail: bouyssou@lamsade.dauphine.fr; tsoukias@lamsade.dauphine.fr T. Marchant () Department of Data analysis, Ghent University, H. Dunantlaan 1, 9000 Gent, Belgium e-mail: Thierry.Marchant@UGent.be M. Pirlot Université de Mons, Faculté Polytechnique, Mons, Belgium e-mail: marc.pirlot@umons.ac.be P. Vincke Université libre de Bruxelles, Ecole Polytechnique, Campus de la Plaine, CP210/01, boulevard du Triomphe, 1050 Bruxelles, Belgium e-mail: Philippe.Vincke@ulb.ac.be © Springer-Verlag Berlin Heidelberg 2015 R. Bisdorff et al. (eds.), Evaluation and Decision Models with Multiple Criteria, International Handbooks on Information Systems, DOI 10.1007/978-3-662-46816-6_3 35