Whereas much of the modeling literature in supply chain planning addresses the analysis of decision models and presents solution techniques and much of the empirical literature on planning systems such as ERP and APS software addresses implementation challenges from an organizational perspective, research on the modeling process of capturing the planning process in planning software is very scarce. In this paper, we examine this modeling process. Our approach is based on a normative method for hierarchical planning and presents a case study where this modeling process was used. We analyze the process, relate it to the literature on modeling, and demonstrate the value of the theory in explaining major observations. We conclude that the hierarchical premise on which most planning processes are based is very difficult to capture in an advanced planning system, and find that users and organizations essentially circumvent this problem by creating their own workflows, independent of the system’s prescribed one.