ABSTRACT
A model is a simplified representation of selected aspects of reality which are of interest to decision makers. In this sense, model development and use are fairly common activities. We use conceptual or mental models (perceptions) to understand, interpret and modify reality in our daily life. Mental models are the most frequently used type and a prerequisite for the existence and use of mathematical models run on a computer. For example, we use maps (iconic models) to plan journeys in an unfamiliar city. As we get to know the city and its transport system better we develop an improved mental map (model) which facilitates more precise and efficient journey planning.
