System Dynamics Community Research Articles

Applying Decision Analysis and System Dynamics Community Governance in the Evaluation of Juvenile Delinquency Prevention Strategies

Abstract From the perspective of juvenile delinquency prevention theory, this paper explores the current situation of juvenile delinquency in rural areas of W County and the mechanism of relevant functional departments in local community governance based on the questionnaire survey method. Then, six juvenile delinquency prevention service programs are selected as the object of evaluation research, and the intelligent decision analysis system of system dynamics is used as the tool of evaluation research to evaluate the six juvenile delinquency prevention programs systematically and comprehensively. The following conclusions were obtained after the analysis. The crime rate of rural youths in County W is as high as 15.8%, with a wide range of crimes. 81.6% of the relevant departments in community governance did not establish rural juvenile records, and about 13% of the departments did not conduct crime prevention training. The Green Clay People Juvenile Crime Prevention Program, which uses social connection theory as a strategy, has an evaluation value of 0.242, and the completion rate of the agreed service indicators specified in the contract is more than 100%. The overall evaluation of the six programs was 87% satisfied. Therefore, the intelligent decision analysis system in this paper has been well applied in the evaluation of juvenile crime prevention strategies, with the progress and development of society, and will occupy an important position in the future for a considerable time.

Trajectory-tracking control from a multibody system dynamics perspective

The development of modern mechatronic systems is often driven by the desire for more efficiency and accuracy. These requirements not only result in more complex system designs, but also in the simultaneous development of improved control strategies. Therefore, control of multibody systems is an active field of research. This contribution gives an overview of recent control-related research from the perspective of the multibody dynamics community. A literature review of the research activity in the journal Multibody System Dynamics is given. Afterwards, the framework of servo-constraints is reviewed, since it is a powerful tool for the computation of a feedforward controller and it is directly developed in the multibody system dynamics community. Thereby, solution strategies for all possible system types, such as differentially flat systems, minimum phase and non-minimum phase systems are discussed. Selected experimental and simulation results are shown to support the theoretical results.

Reflections on adapting group model building scripts into online workshops

Reflections on adapting group model building scripts into online workshops

The Design of Educational Programs in System Dynamics at Worcester Polytechnic Institute (WPI)

Educational programs leading to degrees in system dynamics are rare and thus of critical importance to the future of the field of system dynamics. However, to a large extent such programs have not yet been made transparent to the system dynamics community as a whole. The present article describes the design and rationale for undergraduate and graduate programs at Worcester Polytechnic Institute (WPI). The goal of the article is to invite feedback from the system dynamics community about our specific programs as well as to facilitate wider discussion about the appropriate content, design, and pedagogy of degree programs and courses in system dynamics.

The Design of Educational Programs in System Dynamics at WPI

Educational programs leading to degrees in system dynamics are rare and thus of critical importance to the future of the field of system dynamics. However, to a large extent such programs have not yet been made transparent to the system dynamics community as a whole. The present article describes the design and rationale for undergraduate and graduate programs at WPI. The goal of the article is to invite feedback from the system dynamics community about our specific programs as well as to facilitate wider discussion about the appropriate content, design, and pedagogy of degree programs and courses in system dynamics.

Do parallel lines meet? How can pathway participation metrics and eigenvalue analysis produce similar results?

AbstractThe search for tools and techniques aimed at model analysis has gained momentum in the system dynamics community during the last decade. A variety of approaches have been developed, modified and applied to replace or enhance the traditional intuitive‐based schemes for understanding the behavior of dynamic models according to their feedback structure. In spite of the diversity of the methods developed for model analysis, recent studies suggest that there is considerable convergence in the results they produce. This paper explores the metrics used by the pathway participation approach and eigenvalue elasticity analysis in order to explain how, despite the significant differences in the process of model analysis, they can produce similar and comparable results. The paper discusses the application of pathway participation metrics in four well‐known models that have been previously analyzed using the eigenvalue elasticity method. The case studies highlight some of the similarities and differences between the two approaches in detecting the dominant structure. Copyright © 2009 John Wiley & Sons, Ltd.

Thinking about systems: student and teacher conceptions of natural and social systems

AbstractMany in the system dynamics community argue that children are natural systems thinkers. Here we study how middle school students and teachers think about everyday settings involving feedback, stocks and flows, time delays and nonlinearities, prior to any formal training in these concepts. We develop instruments to elicit understanding of systems concepts and test them with students and teachers from two middle schools in the U.S.A. We find, with some exceptions, generally limited intuitive systems thinking abilities. “Open‐loop” or one‐way causal thinking is common. Explanations lack references to time horizons and time delays. Significant misconceptions of stock and flow structures appear regardless of age. Teachers generally outperformed students, although one‐quarter of the students performed at the median level for teachers. We discuss the nature of students' and teachers' intuitive models of dynamic systems, explore potential barriers to understanding dynamic systems, and discuss implications for effective teaching of systems concepts. Copyright © 2007 John Wiley & Sons, Ltd.

IFORS' Operational Research Hall of Fame Jay Wright Forrester

IFORS' Operational Research Hall of Fame Jay Wright Forrester

XMILE: towards an XML interchange language for system dynamics models

AbstractWe propose that XML should be used as an interchange language for system dynamics models and we have designed and implemented a demonstration that we call XMILE. We believe that there will be many benefits for the system dynamics community in developing a full‐scale interchange language. This paper discusses the motivation factors behind the idea of developing an interchange language for system dynamics models, and explains why XML is a good candidate framework. An initial implementation of XMILE is also presented along with initial findings about its applicability to models built on various system dynamics software platforms. Copyright © 2005 John Wiley & Sons, Ltd.

Don't let history repeat itself—methodological issues concerning the use of simulators in teaching and experimentation

AbstractSimulators can be used for experimentation and for teaching purposes. How far promises of useful applications of simulators in these areas are justified is, however, an open question. Evaluation research on simulators is still in its infancy, both inside and outside the system dynamics community. A reason for this is methodological issues that derive from the nature of experimenting/teaching, but which are also caused by the specific characteristics of simulators. Fifteen such issues are identified and explained in this article and classified into three categories; methods for the mitigation of these issues are discussed. Copyright © 2004 John Wiley & Sons, Ltd.

Selling system dynamics to (other) social scientists

AbstractIn the last decade I have tried to use system dynamics to do research that is acceptable to scholars from other social science communities. In this paper I reflect upon this experience and outline several errors that reduced the accessibility of my work to those outside the system dynamics community. While some of these mistakes are likely unique to me, others are more common to research that uses system dynamics. Acknowledging these errors has several implications for the future organization of the field. Copyright © 2003 John Wiley & Sons, Ltd.

Group model building effectiveness: a review of assessment studies

AbstractOver the last decades system dynamicists have experimented with approaches to achieve more involvement of their clients in the model building process. As a result the number of reports in the literature on the use of system dynamics as an organizational intervention tool has increased dramatically. From the literature we have identified 107 cases that provide details on the modeling process and the assessment of results. The cases show a wide variety in the way the interventions are reported and assessed. From a research point of view this is clearly an undesirable state of affairs. This article reports on a meta analysis of findings of these studies and tries to provide an overview of outcome studies on system dynamics interventions. It attempts to draw some preliminary conclusions on the effectiveness of system dynamics modeling interventions, to clarify differences in definitions of outcomes, and to provide guidelines for more standardized assessments and reports. Rather than remaining in the stage of single case descriptions, the latter will enable the accumulation of research results in the future, a prerequisite for institutional learning within the system dynamics community. Copyright © 2002 John Wiley & Sons, Ltd.

Should system dynamics be described as a ?hard? or ?deterministic? systems approach?

This paper explores the criticism that system dynamics is a ‘hard’ or ‘deterministic’ systems approach. This criticism is seen to have four interpretations and each is addressed from the perspectives of social theory and systems science. Firstly, system dynamics is shown to offer not prophecies but Popperian predictions. Secondly, it is shown to involve the view that system structure only partially, not fully, determines human behaviour. Thirdly, the field's assumptions are shown not to constitute a grand content theory—though its structural theory and its attachment to the notion of causality in social systems are acknowledged. Finally, system dynamics is shown to be significantly different from systems engineering. The paper concludes that such confusions have arisen partially because of limited communication at the theoretical level from within the system dynamics community but also because of imperfect command of the available literature on the part of external commentators. Improved communication on theoretical issues is encouraged, though it is observed that system dynamics will continue to justify its assumptions primarily from the point of view of practical problem solving. The answer to the question in the paper's title is therefore: on balance, no.

Mental models concepts for system dynamics research

Although “mental models” are of central importance to system dynamics research and practice, the field has yet to develop an unambiguous and agreed upon definition of them. To begin to address this problem, existing definitions and descriptions of mental models in system dynamics and several literatures related to cognitive science were reviewed and compared. Available definitions were found to be overly brief, general, and vague, and different authors were found to markedly disagree on the basic characteristics of mental models. Based on this review, we concluded that in order to reduce the amount of confusion in the literature, the mental models concept should be “unbundled” and the term “mental models” should be used more narrowly. To initiate a dialogue through which the system dynamics community might achieve a shared understanding of mental models, we propose a new definition of “mental models of dynamic systems” accompanied by an extended annotation that explains the definitional choices made and suggests terms for other cognitive structures left undefined by narrowing the mental model concept. Suggestions for future research that could improve the field's ability to further define mental models are discussed. © 1998 John Wiley & Sons, Ltd.

Formal aspects of model validity and validation in system dynamics

Model validation constitutes a very important step in system dynamics methodology. Yet, both published and informal evidence indicates that there has been little effort in system dynamics community explicitly devoted to model validity and validation. Validation is a prolonged and complicated process, involving both formal/quantitative tools and informal/qualitative ones. This paper focuses on the formal aspects of validation and presents a taxonomy of various aspects and steps of formal model validation. First, there is a very brief discussion of the philosophical issues involved in model validation, followed by a flowchart that describes the logical sequence in which various validation activities must be carried out. The crucial nature of structure validity in system dynamics (causal-descriptive) models is emphasized. Then examples are given of specific validity tests used in each of the three major stages of model validation: Structural tests, structure-oriented behavior tests and behavior pattern tests. Also discussed is if and to what extent statistical significance tests can be used in model validation. Among the three validation stages, the special importance of structure-oriented behavior tests is emphasized. These are strong behavior tests that can provide information on potential structure flaws. Since structure-oriented behavior tests combine the strength of structural orientation with the advantage of being quantifiable, they seem to be the most promising direction for research on model validation.

Formal aspects of model validity and validation in system dynamics

Model validation constitutes a very important step in system dynamics methodology. Yet, both published and informal evidence indicates that there has been little effort in system dynamics community explicitly devoted to model validity and validation. Validation is a prolonged and complicated process, involving both formal/quantitative tools and informal/qualitative ones. This paper focuses on the formal aspects of validation and presents a taxonomy of various aspects and steps of formal model validation. First, there is a very brief discussion of the philosophical issues involved in model validation, followed by a flowchart that describes the logical sequence in which various validation activities must be carried out. The crucial nature of structure validity in system dynamics (causal-descriptive) models is emphasized. Then examples are given of specific validity tests used in each of the three major stages of model validation: Structural tests, structure-oriented behavior tests and behavior pattern tests. Also discussed is if and to what extent statistical significance tests can be used in model validation. Among the three validation stages, the special importance of structure-oriented behavior tests is emphasized. These are strong behavior tests that can provide information on potential structure flaws. Since structure-oriented behavior tests combine the strength of structural orientation with the advantage of being quantifiable, they seem to be the most promising direction for research on model validation.

Benchmarking the system dynamics community: Research results

AbstractThis article reports on the findings of a wide‐ranging study designed to ‘benchmark’ the system dynamics community. The study captured information about individual practitioners across a number of dimensions, including background, approach to and practice of model building, use of hardware and software and knowledge of the history and development of the field. Circulated to all members of the System Dynamics Society, the study attracted responses from 163 members (over 35 percent). The following pages present research results and discuss their possible implications. In particular, important conclusions highlight a potential quality gap in the model base, postulate a relationship between pedagogy and practice and begin a dialog concerning the dynamics of supply and demand in the field.

On a Resurgence of Management Simulations and Games

The past few years have seen a significant resurgence of interest in ‘management games’ and ‘management flight simulators’, one particularly active source of such work being the system dynamics community. After proposing a distinction between games and simulations, this paper provides some background to these developments by briefly describing the historical roots of the field and the fundamental ideas of the system dynamics community, which are now giving rise to ‘microworlds’. The training advantages of management simulations and games are then discussed. The paper closes with a note on the research and findings of the system dynamics field and by offering some words of warning on the perils of simulation and game use. Two scenarios for how the use of simulations and games as management education devices might develop in the future are proposed. An Appendix describes five examples of very different types of management simulations and games.

Systems thinking/system dynamics: Let's just get on with it

AbstractThe world has many problems. Many of these problems are approaching crisis proportions. The system dynamics community has something very powerful to contribute to addressing these problems—whether we call that something systems thinking or system dynamics. We have not been very effective in sharing what we have to offer because we have failed to truly appreciate the essence of system dynamics. As a result, we have both consciously and unwittingly diluted this essence, and in the process made more difficult the task of disseminating what we have to offer. We need to better understand and appreciate the essence of our field and then focus our energies on the real task at hand: figuring out why this essence seems to be so difficult for people to grasp, and then fixing that.

Conference calendar

AbstractThis section of the System Dynamics Review is an eclectic source of information on items of interest to the system dynamics community. Conferences, articles, books, dissertations, speeches, software and hardware products, and teaching materials are mentioned in this space. The purpose of the section is to provide summaries to help the system dynamics community keep abreast of recent progress related to the field and to anticipate important future events. Submissions covering a wide range of areas and information of possible interest to system dynamicists are encouraged and should be sent to R. Joel Rahn, Faculté des Sciences de l'Administration, Université Laval, Ste. Foy, Quebec, G1K 7P4, Canada. Fax: (418) 656‐2624. E‐mail: rahnj@vml.uiaval.ca.