PROMETHEE and GAIA belong to the family of outranking methods as it was initiated by Bernard Roy at the end of the sixties with the ELECTRE methods. Outranking methods provide decision makers with an alternative to the aggregation methods that are popular in the US and the UK. Typically they require less information from the decision maker(s) and allow to keep closer to the actual decision problem.
The original PROMETHEE methods have been conceived by Jean-Pierre Brans in 1982. With respect to the contemporary ELECTRE methods (ELECTRE III and IV) they brought at the same time more flexible preference modeling capabilities and a greater ease of use.
From the middle of the eighties the development of powerful interactive sensitivity analysis tools has been central to the evolution of the PROMETHEE methods. More specially the weighing of the criteria is known to play a major role in MCDA. It is thus essential for decision makers to be able to see to what extent changes of the weights of the criteria will impact the rankings provided by a multicriteria method. The PROMETHEE methods include several unique tools for this purpose such as the weight stability intervals and the Walking Weights interactive procedure.
In 1989 the introduction of GAIA added a descriptive complement to the PROMETHEE rankings. A graphical representation of the multicriteria problem enables the decision maker to better understand the available choices and the necessary compromises he or she will have to make to achieve a best decision. GAIA can also be used to see the impact of the criteria weights on the PROMETHEE rankings.
GDSS (group decision support system) extensions of PROMETHEE and GAIA have also been developed and integrated in the PROMETHEE Software. They enable to compare the points of view of different decision-makers, to analyze conflicts between decision-makers and to generate consensus decisions.
The PROMETHEE and GAIA methods have been widely applied since their first appearance in 1982. The Visual PROMETHEE software includes the basic methods as well as several newer developments.