D-4500-5 1 Road Maps A Guide to Learning System Dynamics 0 System Dynamics in Education Project2 A Guide to Learning System Dynamics D-4500-5 Road Maps 0 System Dynamics in Education Project System Dynamics Group Sloan School of Management Massachusetts Institute of Technology June 21, 1992 June 21, 2000 Revised December 20, 2002 Copyright © 1994 by MIT Permission granted to copy for non-commercial educational purposes Macintosh is a registered trademark of Apple Computer, Inc. STELLA, STELLA II and iThink are trademarks of High Performance Systems. Vensim and Vensim PLE are trademarks of Ventana Systems Inc. Compiled under the direction of Professor Jay W. Forrester3 D-4500-5 Road Maps Welcome to Road Maps! Many books and thousands of papers cover the field of system dynamics. With all of these resources available, it is difficult to know where to begin learning about system dynamics. The System Dynamics in Education Project at MIT is putting together Road Maps to help sort through this vast library of books and papers. Road Maps is a series of self-study guides that use modeling exercises and selected literature to provide a resource for learning about the principles and practices of system dynamics. In its present form, Road Maps is not meant to be a teaching curriculum for classroom use. The Spiral Learning Approach A new concept is usually not fully mastered after reading about it only once. Also, learning usually involves building one’s understanding up from one level to a higher level. For this reason, Road Maps utilizes a spiral learning approach, in which each new concept is repeatedly reinforced in successive chapters. This repetition moves upward along a spiral as more advanced concepts build upon basic ones. In constructing this spiral, Road Maps has been divided into chapters. The end of each chapter marks the completion of a particular subset of concepts, with the next chapter building on the material just learned. Each chapter comes as a separate document so the reader can request them as needed.4 A Guide to Learning System Dynamics D-4500-5 Organization The Road Maps series begins with Road Maps One, which introduces the concepts of causal loops and circular feedback in systems. In addition, some of the applications and history of system dynamics are presented. Road Maps Two takes you through your first system dynamics models, introducing computer simulation and the concept and methods of graphical integration. Two basic elements of system dynamics models, the stock and flow, are presented. You will need a computer and STELLA� or Vensim� software for this and subsequent chapters of Road Maps. Road Maps Three presents two of the most common structures in system dynamics: the first-order positive and negative feedback loops. Systems exhibiting exponential growth and decay are examined, and the idea of loop dominance in systems is introduced Road Maps Four introduces generic structures and discusses the use of computer simulation games in teaching system dynamics. After playing the Fish Banks game, you will construct a model of the scenario and learn about the tragedy of the commons. Using your computer model, you will simulate and analyze several policies for this system. Road Maps Five probes the structure of system dynamics models, emphasizing some important features that you may not have noticed, and explains the spread of an epidemic. Road Maps Five also introduces testing for model validity in the system dynamics context. How do you know that your model is a good representation of the real system? In Road Maps Six, the dynamics of economic supply and demand are explored and more modeling exercises are provided. Also, oscillatory systems are used to show the transferability of structures. More modeling exercises sharpen your modeling skills and develop intuition about systems. Road Maps Seven presents some unexpected behaviors that can occur in higher-order positive feedback loops. It also points out mistakes commonly found in system dynamics models and provides more independent modeling exercises. Road Maps Eight continues to improve your modeling skills by analyzing the first stage of the process of building a model: conceptualization, and by warning you against other mistakes commonly made in models. Road Maps Eight5 D-4500-5 Road Maps also increases your understanding of oscillating systems and introduces sensitivity analysis. Road Maps Nine explores the dynamics of credit card spending, illustrates how to correctly formulate table functions, and introduces the behavior known as overshoot and collapse. More graphical integration exercises develop your intuitive understanding of the process of graphical integration. Road Maps Ten provides further instruction on how to build a model from scratch with exercises for the second step, formulation. There are a number of other papers in Road Maps Ten which will continue to build skill in working with system dynamics models and continue the reader's understanding of system dynamics principles. Road Maps discusses the principles and characteristics of systems, explores the interrelationship between structure and behavior of dynamic models, provides guidelines for good modeling practice, and discusses the applications of system dynamics. From Road Maps One on, the spiral of learning returns to these primary areas several times by introducing more advanced material while building on fundamental concepts. After completing Road Maps, you should have a strong working knowledge of system dynamics, have developed intuition about the fundamental principles of systems and be ready to explore the application of system dynamics in any area of interest. How to Use Road Maps First, you need to determine where you should begin in Road Maps. Some readers have had more background in system dynamics than others. This introduction should help you find a good starting point in Road Maps. Road Maps explores several topics in system dynamics through selected readings and exercises. Before each reading or exercise is a short description of the reading and its most important ideas. After each reading or exercise, we highlight the main ideas before moving on. Each chapter in Road Maps contains readings that introduce and strengthen some of the basic concepts of system dynamics. Other readings focus on practicing the acquired skills through various exercises or simulation games. Most6 A Guide