We describe a three-pass algorithm for improving the readability of Forrester Diagram in system dynamics. The first pass converts Forrester Diagram to recurrent hierarchy. The second pass sorts the vertices on each level, with the goal of minimizing crossings. The third pass is a finite tuning of the layout that determines the horizontal positions of vertices. An illustrative example is given to verify the result. | Yugoslav Journal of Operations Research 13 (2003), Number 1, 107-130 A TECHNIQUE FOR IMPROVING READABILITY OF FORRESTER DIAGRAM IN SYSTEM DYNAMICS Wei-Tzen YANG Graduate Institute of Management Sciences Tamkang University, Tamsui, Taipei Hsien, Taiwan 25137 g5450022@ Nai-Wen KUO Department of Information Management Chinese Culture University, Yang Ming Shan, Taipei, Taiwan 111 chingneven@ Abstract: We describe a three-pass algorithm for improving the readability of Forrester Diagram in system dynamics. The first pass converts Forrester Diagram to recurrent hierarchy. The second pass sorts the vertices on each level, with the goal of minimizing crossings. The third pass is a finite tuning of the layout that determines the horizontal positions of vertices. An illustrative example is given to verify the result. Keywords: System Dynamics (SD), Forrester Diagram (FD), recurrent hierarchies, readability, algorithm. 1. INTRODUCTION System Dynamics (SD), developed by Forrester [1], is useful in the study of continuous dynamical system, which has been mainly applied to the simulation of social and managerial systems [1, 3, 5, 9-14, 16, 20]. Simulation packages such as DYSMAP, STELLA and I-THINK are used in system dynamics helping to formulate the data flow of system and to simulate the results of models for user. But, whenever system is fluctuating or the size of problems becomes larger, it is difficult to manipulate Forrester Diagram (FD) by the modeler. Generally speaking, it is difficult to analyze the structure of a digraph readily unless vertices are laid out in some regular form edges are drawn in such a form that paths can be readily traced by human eyes. To consider common aspects of readability we can base it on the following aesthetic principles: 1. Hierarchical layout of vertices. 2. Avoid edge crossing and sharp bends. 108 . Yang, . Kuo / A Technique for Improving Readability of Forrester Diagram 3. 4. Keep edges .
