Using free modeling as an Agile method for developing domain specific modeling languages

International audience; Mostly the development of domain specific modeling languages (DSML) follows the traditional model driven engineering practices. First the syntax and semantics of the language are defined (at meta-level) and then it is used for the development of user models. In certain situations, it is hard even to conceptualize the demands of the user, let alone the definition of the language. Agile methods for software development suggest that the development activities should be performed alongside a client stakeholder for incremental development of the system. This approach helps in the elicitation of requirements in parallel to the actual development of the system. We followed this approach for developing a domain specific modeling language and its tooling for a local government project, Brest Métropole. The project aimed at filling the communication gap between the elected representatives (politicians) and the bureaucracy (government officers). We used a modeling methodology that does not restrict a modeler's interaction to a single abstraction level. Thus a modeler can develop both models and metamodels at the same time, where the definition of one helps in defining the other. In this article, we explain our experiences from this project and share the lessons learnt.