A requisite decision model is defined as a model whose form and content are sufficient to solve a particular problem. The model is constructed through an interactive and consultative process between problem owners and specialists (decision analysts). The process of generating the model uses participants' sense of unease about current model results to further development of the model. Sensitivity analyses facilitate the emergence of new intuitions about the problem; when no new intuitions arise, the model is considered requisite. At all stages of development, the model represents the social reality of the shared understanding of the problem by the problem owners. The goal of creating a requisite model is to help construct a new reality, to create a future. Validating a requisite decision model is done with reference to a requisite validation model whose form will be recognizably multi-attributed and whose content may draw on a variety of disciplines both scientific and clinical. A requisite model is more likely to be adequate if problem owners contributing to its development represent a variety of views, if the adversarial process is used to advantage, and if the specialist can provide a neutral perspective and setting. The role of decision analysis is to provide a framework for the development of a coherent model and to provide structure to thinking. While requisite models may be applicable in other areas of social science, they certainly highlight the need for a psychology of what people can do.
