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Introduction to decision aid

Outranking methods

The outranking decision aid methods compare all couples of actions. Instead of building complex utility functions, they determine which actions are being preferred to the others by systematically comparing them on each criterion, using the same principle as the Condorcet's method.

The comparisons between the actions lead to numerical results that show the concordance and/or the discordance between the actions, and then allow to select or to sort the actions that can be compared.

The first well known outranking method is called Electre, and DECIDE includes several functions related to the calculations used in this method. Another well known outranking method is called Promethee.

DECIDE fully implements this method, including it's major developments (Promethee I, II and III), as well as a new and unique 3-dimensional representation of the actions and the criteria called SpatialGAIA, based on GAIA by Mareschal & Brans 1988.

The DECIDE demonstration workbook even includes the DECIDE wizard that creates a new worksheet for you with all the Promethee calculations: you just need to supply the number of actions and criteria, and the wizard does all the work for you... Other free implementations of Promethee using Euler and Mathcad are available here.

As portable library of functions, DECIDE cannot directly interact with the hardware to display graphics. However, it can compute the required data to allow the display of the GAIA visualization, using whatever software is required on the user's hardware.

A separate program called SpatialGAIA, running under Windows is included in the DECIDE installation package.

External programs used to display the GAIA visualization need to call DECIDE__Gaia() to obtain the GAIA data for the last problem resolved with one of the Promethee methods.


Electre (ELimination Et Choix Traduisant la Realité) is a well known outranking decision aid method, originally developed in France by Bernard Roy around 1968. It has been declined in several versions (mainly I, II, III, IV and IS). Versions I and IS are used for the selection of actions, while II, III and IV are used for the classification of actions.

DECIDE features several functions directly related to the calculations made for Electre. See DECIDE__DecisionMatrixFlows() for details.


Promethee (Preference Ranking Organisation METHod for Enrichment Evaluations) is another well known outranking decision aid method, originally developed in Belgium by JP Brans around 1984.

Promethee is very intuitive and easy to use. DECIDE fully implements this method and its developments (like GAIA), and even features new tools like the 3D view of the GAIA plane, the 3D representation of the Promethee axis and an original view called PDV (Plan De Visée). The graphical display is made with an external utility supplied with DECIDE, and called SpatialGaia.

Furthermore, all these features can be accessed without effort by using the DECIDE wizard supplied with the DECIDE demonstration workbook.

See DECIDE__Promethee() for details.

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