In ELECTRE methods, the construction of an outranking relation amounts at validating or invalidating, for any pair of alternatives (a,b), the assertion “a is at least as good as b”. This comparison is grounded on the evaluation vectors of both alternatives, and on additional information concerning the decision maker's preferences, accounting for two conditions: concordance and non-discordance. In decision processes using these methods, the analyst should interact with the decision maker in order to elicit values for preferential parameters. This can be done either directly or through a disaggregation procedure that infers the parameters values from holistic judgements provided by the decision maker. Inference is usually performed through an optimization program that accounts for the aggregation model and minimizes an “error function”. Although disaggregation approaches have been largely used in additive models, only few advances have been made towards a disaggregation approach for outranking methods. Indeed, outranking methods may lead to computationally difficult inference problems. In this paper we are concerned with a slight adaptation of the valued outranking relation used in the ELECTRE III and ELECTRE TRI. Such modification is shown to preserve the original discordance concept. We show that the modified outranking relation makes it easier to solve inference programs.
