Interfacing Large Interactive Systems Models and the User: The Case of a Beef Cattle Enterprise Model for Decision Assistance

The interface between a large interactive simulation model and the user is discussed along with and in the context of a general beef cattle enterprise model designed to be used as a decision assistance tool. Emphasis in this model is on the cow/calf land extensive form of operation. A highly disaggregated herd population model allows full exploration of population dynamics. Using total digestible nutrients (TDN) as the basic feed quality description, and net energy for growth and maintenance where possible, the nutrient impact component predicts rates of weight gain and reproductive dynamics as a function of feed intake. Forage growth is modeled as a function of the exogenous variables of solar radiation, temperature, and rainfall. As an enterprise model, attention is focused on the planning and management decisionmaking needs of decisionmakers. The model is viewed as a tool for exploration of alternative strategies to assist the traditional and intuitive method of management. The model is interactive, with straightforward decisions made using endogenous decision rules, while complex decisions require the input of the model user. The design of the interface between the model and the user to allow effective interaction is discussed in detail. A demonstration of the model´s capability is given using a project investment planning example.