Du 3 59

Many decisions can be affected by certain types of interaction effects among and between some criteria of a coherent family of criteria, as for example, those resulting from a synergy or a redundancy phenomenon. However, in real-world decision aiding situations the relevant interactions (which should be modeled) are those that generally occur only between a small number of criteria pairs. Presently there is only a few number of methods to deal with such interaction effects. These interactions should thus be taken into account when comparing two different actions or projects. The interaction between pairs of criteria is of a very particular importance in the field of assessing sustainable development. The purpose of this paper is to study the applicability of the ELECTRE III method with interaction between pairs of criteria. In order to reach this objective, we are interested in the ranking of five alternative projects, compared on the basis of six different criteria, for the requalification of an abandoned quarry located in Northern Italy. A focus group of experts (in economic evaluation, environmental engineering, and landscape ecology) has been constituted with the aim of being in charge of the process leading to the assignment of numerical values to the weights and the interaction coefficients. We relate on the way the process evolved and on the difficulties that we have encountered to obtain consensual sets of values. Taking into account these difficulties we have considered other sets of weights and interaction coefficients. Our aim was to study the impact on the final ranking of the fact that these numerical values, assigned to the parameters, were not perfectly defined. This allowed us to formulate robust conclusions which have been then presented to the members of the focus group.