The farmer's decisional process is generated by the fit or the misfit between farmer's goals and his actual working situation. Understanding the informational activity (i.e. what occurs before the final decision) is a major stake to better understand the decisional process and then to be able to help farmers to take the "good" one. We assume that modelling the farmers' informational activity to be able to represent the diversity of how they take their decision, is an appropriate methodology. In this perspective, we propose to model the informational activity by using a pyramidal diagram linking four elements: the farmer, the fields concerned by the farming activity, the events concerned by the decisions and the informational resources. Four hypotheses are tested to explain the different relationships within this analysis framework and then the whole system of information. We present i) the different elements relevant for understanding the structure and the functioning of the system; ii) the different criteria explaining how the system is activated by different kind of events. These two kinds of results will be mobilised with our partners of working in advising structures to think about new ways and methodologies to reach farmers' requirements.