D-4508-2 1 Road Maps 8 A Guide to Learning System Dynamics System Dynamics in Education Project2 A Guide to Learning System Dynamics D-4508-2 Road Maps 8 System Dynamics in Education Project System Dynamics Group Sloan School of Management Massachusetts Institute of Technology July 1, 1997 Latest Revision March 18, 2001 Copyright © 2001 by MIT Permission granted to copy for non-commercial educational purposes STELLA, STELLA II and ithink are trademarks of High Performance Systems Macintosh is a trademark of Apple Computers, Inc. Compiled under the direction of Professor Jay W. Forrester3 D-4508-1 Road Maps 8 Welcome to Road Maps Eight! Road Maps is a self-study guide to learning the principles and practice of system dynamics. This chapter is the eighth in the Road Maps series. Road Maps One through Three give a broad introduction to the field of system dynamics, focusing on understanding the structure and behavior of systems through positive and negative feedback loops. Road Maps Four through Six introduce several generic structures, give a taste of policy analysis and model validity, and provide opportunities for independent modeling. Road Maps Seven presents some unexpected behaviors that can occur in higher-order positive feedback loops. Also, Road Maps Seven contains the first paper explaining common mistakes and misunderstandings in system dynamics modeling. The chapter offers more independent modeling exercises, and explains “reverse” graphical integration. Road Maps Seven concludes with a paper on the relationship of systems thinking and soft operations research to system dynamics. In Road Maps Eight we begin a series of papers on the model-building process with an analysis of the conceptualization stage of building a system dynamics model. The second mistakes and misunderstandings paper warns against an incorrect use of generic structures and emphasizes the real nature of stocks and flows. Road Maps Eight continues with a detailed explanation of the structural causes of sustained oscillation, and presents the first in a series of papers on sensitivity analysis. The chapter ends with a transcription of a speech by Prof. Jay Forrester given at the Systems Thinking and Dynamics Modeling Conference for K-12 Education in June 1994. Topics Covered in Road Maps Eight Improving Modeling Skills - Building a System Dynamics Model Part 1: Conceptualization (D-4597) by Stephanie Albin4 A Guide to Learning System Dynamics D-4508-2 - Mistakes and Misunderstandings: Use of Generic Structures and Reality of Stocks and Flows (D-4646) by Lucia Breierova Oscillation - Oscillating Systems II: Sustained Oscillation (D-4602) by Kevin Agatstein Sensitivity Analysis - An Introduction to Sensitivity Analysis (D-4526) by Lucia Breierova and Mark Choudhari System Dynamics in Education - Learning through System Dynamics as Preparation for the 21st Century (D-4434-1) by Jay W. Forrester Things You’ll Need for Road Maps Eight Modeling Software In order to complete Road Maps Eight and subsequent Road Maps, you will need to have access to modeling software. The Road Maps guides and most papers included in Road Maps were written with the use of STELLA II for the Macintosh. STELLA II is currently available for both the Macintosh and the Windows platforms. If you have any questions about STELLA, contact High Performance Systems (see Appendix). Ask about prices for educational use. Vensim, Powersim, and DYNAMO are other software programs designed for building system dynamics models. Vensim is produced by Ventana Systems, which offers a free introductory version of its software, Vensim PLE, that can be downloaded off the World Wide Web. See the Appendix for more information about obtaining Vensim and Powersim. Notice written June, 2000: We have written a guide on how to use Vensim modeling software for each section of the Road Maps series that involves computer modeling. Each guide is5 D-4508-1 Road Maps 8 located in the back of the exercise document. When Chapters 1-9 of the Road Maps series were written, STELLA software was the most common beginner modeling program available. Now you may choose from a number of system dynamics modeling software packages. If you would like more information on Vensim, please go to http://www.vensim.com. A free version called Vensim PLE is located there. For more detailed information on using Vensim software in the Road Maps series, please refer to the paper titled: “Vensim Guide (D-4856)” in the Appendix section at the end of Road Maps. From now on as additional papers for the Road Maps series are written, the Vensim software will be used exclusively for modeling exercises. A Computer To run the latest version of STELLA, STELLA 5.0, on a Macintosh, you will need an Apple Macintosh computer (68020 processor or higher) with at least 8 MB of RAM, a 12 MB hard disk and System 7.1 or higher. To run STELLA 5.0 for Windows you will need an IBM PC-compatible computer with a 486-class processor running Windows 3.1 or greater. You will need at least 8 MB RAM, a hard disk with a least 16 MB of free space. Previous versions of STELLA have similar requirements. In either case, if you plan on continuing to model, it may be a good idea to have access to a computer with more memory, hard disk space and a faster processor. Books You will need the following book for Road Maps Eight. The book was previously required in Road Maps. Goodman, Michael R., 1974. Study Notes in System Dynamics. Portland, Oregon: Productivity Press, 388 p. If you have any problems in getting this book, contact Productivity Press (see Appendix).6 A Guide to Learning System Dynamics D-4508-2 How to Use Road Maps Eight Road Maps Eight 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. Many of the chapters conclude with a prominent paper from the literature in the field of system dynamics. As part of the spiral learning approach used in Road Maps, many concepts will be briefly introduced early on and then explained later in greater