Companion modelling (ComMod)

Companion modelling, ComMod for short (in French, modélisation d'accompagnement), is a way of building a model of how people share a renewable resource, such as land, water or forest, together with the people concerned.^1,2 The main tools are role-playing games and agent-based models, computer simulations in which each farmer, herder or household is a separate actor with its own rules.^1,2 In practice a researcher draws up a first model of how the place works, puts it in front of the people concerned through simulations or role-playing games, and revises or rebuilds it from what they say and do.¹ The cycle of field work, modelling, simulation and field work again repeats, and leaves a family of models rather than one finished one.¹

The approach was set out in 2003 as a charter in the Journal of Artificial Societies and Social Simulation.^1,3 Its twelve signatories came from CIRAD, Cemagref, INRA, the Tour du Valat and the IFB.¹ Among them were the CIRAD modellers François Bousquet and Christophe Le Page, the Cemagref water scientist Olivier Barreteau and the INRA plant ecologist Michel Etienne.¹ A French version was finalised in 2004, and a shorter text for a wider audience in 2013.³ The charter calls it a scientific stance rather than a modelling handbook, and the model "merely an intermediary object" for shared thinking.¹

The charter gives it two uses. One is to understand a system: researchers and local people learn together, and the model seeks "a mutual recognition of everyone representation" of the problem rather than simplifying what people know.¹ The other is to support a collective decision, by making each party's points of view and criteria explicit.¹ Here the charter says the aim is not the best solution but a better process, and that the scientific view is one among others.¹ Every assumption behind the model is meant to be discarded after each round in the field, which is to say put up for refutation.¹

The group's main book in English is Companion Modelling: A Participatory Approach to Support Sustainable Development, edited by Michel Étienne (Springer, 2014, copyright Éditions Quae).⁵ A French collective book on the approach came out from Quae in 2010.² The English book's chapters cover models for sharing representations, power imbalances between participants, assessing the effects, and passing the approach on. It includes 27 case studies and 7 teaching tools.⁵ The ComMod association runs a discussion forum and regular training schools; the 2026 school was held in Montpellier from 7 to 11 September with 13 participants.^2,4 Cormas, CIRAD's agent-based modelling platform for relations between societies and their environment, is close to the group: the charter asked new signatories to register through the Cormas website, and the Cormas site offers the approach.^1,6 Cormas is free under the MIT licence.⁶

Here the people concerned meet the model while it is still being built, and what they say and do in the game changes it.