This article aims to develop several aspects of the current problems associated with the design of decision support systems of the type ODSS (Organisational Decision Support System). However, the design of a decision-making tool must go through a crucial phase and upstream which is the formalization of the process of decision making. Among the available models for the implementation of a decision process, we include the IDC Standard (Intelligence Design Choice), which is, in our opinion, the best suited to the case. However, the latter has limitations in its decision-making strategy. The aim of this paper is to propose an approach to decision making based on this standard, by extending it through the addition of two additional phases. This essay presents the advantage of providing a more coherent and retrospective vision in the specification of decision making. We illustrate this contribution by the formalization of a situation of decision, namely: Response to Tender (RAO). The latter will be treated to resolve the issue of choice of industrial processes. We will try in the future to apply it to the processes of wastewater treatment.