PROMETHEE and GAIA in a multi-decision maker environment

PROMETHEE and GAIA are multicriteria decision aidmethods that have been developed a few years ago with the outranking approach. Today we feel more and more that such methods sometimes are not well suited to the problem studied, because there is not only one decision maker but several. That is why new classes of decision support system are born: GDSS, NSS, ... In this framework, PROMETHEE and GAIA have been adapted allowing them to treat multi-decision maker problems. They provide powerful tools to analyse the relations between criteria or between decision makers, to estimate the distance to a consensus, to point out interesting directions for group discussions, etc. Emphasis is put on visual tools.