This paper gives an introduction to this issue, and presents the framework and the main steps of the Rosa project. Four teams of researchers, agronomists, computer scientists, psychologists and linguists were involved during five years within this project that aimed at the development of a knowledge based system. The purpose of the Rosa system is the modelling and the comparison of farm spatial organizations. It relies on a formalization of agronomical knowledge and thus induces a joint knowledge building process involving both the agronomists and the computer scientists. The paper describes the steps of the modelling process as well as the filming procedures set up by the psychologists and linguists in order to make explicit and to analyze the underlying knowledge building process.