Construction by replacement: a new approach to simulation modeling

Simulation modeling can be valuable in many areas of management science, but it is often costly, time-consuming, and difficult to do. To reduce these problems, system dynamics researchers have previously developed standard pieces of model structure, called molecules, that can be reused in different models. However, the models assembled from these molecules often lacked feedback loops and generated few, if any, insights. This paper describes a new and more promising approach to using molecules in system dynamics modeling. The heart of the approach is a systematically organized library (or taxonomy) of predefined model components, or molecules, and a set of software tools for replacing one molecule with another. Users start with a simple generic model and progressively replace parts of the model with more specialized molecules from a systematically organized library of predefined components. These substitutions either create a new running model automatically or request further manual changes from the user. The paper describes our exploration using this approach to construct system dynamics models of supply chain processes in a large manufacturing company. The experiment included developing an innovative "tangible user interface" and a comprehensive catalog of system dynamics molecules. The paper concludes with a discussion of the benefits and limitations of this approach. Copyright (C) 2010 System Dynamics Society.