Showing papers by "Michael North published in 2006"

Experiences creating three implementations of the repast agent modeling toolkit

Abstract: Many agent-based modeling and simulation researchers and practitioners have called for varying levels of simulation interoperability ranging from shared software architectures to common agent communications languages. These calls have been at least partially answered by several specifications and technologies. In fact, Tanenbaum [1988] has remarked that the “nice thing about standards is that there are so many to choose from.” Tanenbaum goes on to say that “if you do not like any of them, you can just wait for next year's model.” This article does not seek to introduce next year's model. Rather, the goal is to contribute to the larger simulation community the authors' accumulated experiences from developing several implementations of an agent-based simulation toolkit. As such, this article focuses on the implementation of simulation architectures rather than agent communications languages. It is hoped that ongoing architecture standards efforts will benefit from this new knowledge and use it to produce architecture standards with increased robustness.

Tutorial on agent-based modeling and simulation part 2: how to model with agents

Abstract: Agent-based modeling and simulation (ABMS) is a new approach to modeling systems comprised of interacting autonomous agents. ABMS promises to have far-reaching effects on the way that businesses use computers to support decision-making and researchers use electronic laboratories to do research. Some have gone so far as to contend that ABMS is a new way of doing science. Computational advances make possible a growing number of agent-based applications across many fields. Applications range from modeling agent behavior in the stock market and supply chains, to predicting the spread of epidemics and the threat of bio-warfare, from modeling the growth and decline of ancient civilizations to modeling the complexities of the human immune system, and many more. This tutorial describes the foundations of ABMS, identifies ABMS tool-kits and development methods illustrated through a supply chain example, and provides thoughts on the appropriate contexts for ABMS versus conventional modeling techniques.

Evaluating the potential impact of transmission constraints on the operation of a competitive electricity market in Illinois.

Abstract: Despite the current adequacy of the generation and transmission system in Illinois, there is concern that the uncertainties of electricity restructuring warrant a more detailed analysis to determine if there might be pitfalls that have not been identified under current conditions. The problems experienced elsewhere in the country emphasize the need for an evaluation of how Illinois might fare under a restructured electricity market. The Illinois Commerce Commission (ICC) commissioned this study to be undertaken as a joint effort by the University of Illinois at Urbana-Champaign and Argonne National Laboratory to evaluate the Illinois situation in the 2007 period when restructuring is scheduled to be fully implemented in the State. The purpose of this study is to make an initial determination if the transmission system in Illinois and the surrounding region would be able to support a competitive electricity market, would allow for effective competition to keep prices in check, and would allow for new market participants to effectively compete for market share. The study seeks to identify conditions that could reasonably be expected to occur that would enable a company to exercise market power in one or more portions of the State and thereby create undue pressure on themore » prices charged to customers and/or inhibit new market participants from entering the market. The term 'market power' has many different definitions, and there is no universal agreement on how to measure it. For the purposes of this study, the term is defined as the ability to raise prices and increase profitability by unilateral action. A more complete definition is provided later. With this definition, the central question of this analysis becomes: 'Can a company, acting on its own, raise electricity prices and increase its profits?' It should be noted that the intent of the study is not to predict whether or not such market power would be exercised by any company. Rather, it is designed to determine if a set of reasonably expected conditions could allow any company to do so. It should also be emphasized that this study is not intended to be a comprehensive evaluation of the electric power system in the State. Rather, it is intended to identify some issues that may impact the effective functioning of a competitive market.« less

Containing agents : contexts, projections, and agents.

Abstract: Agent-based models have historically maintained a tight coupling between individuals, their behaviors, and the space in which they interact As a result, many models have been designed in a way that limits their ability to express behaviors and interactions In this paper, we propose a new approach toward designing simulations that builds upon the experiences of developing and working with several agent-based toolkits This approach encourages flexibility and reusability of components and models A preliminary implementation is the core structure of the upcoming Repast Simphony agent-based modeling and simulation toolkit By creating a 'proto-space' called a Context, we provide model designers with a container that can maintain a localized state for agents A Context's state can maintain multiple interaction spaces called Projections, as well as more typical state information Projections are designed such that they can be used to represent a wide range of abstract spaces, from graphs to grids to realistic geographic spaces Importantly, projections and agents or individuals are independent of one another Agents can be agnostic toward the type of projection in which they are interacting, and projections can be agnostic toward the type of agents whose relationships they maintain Finally, the context provides a logical locationmore » to maintain agent behaviors that are dependent on localized agent interactions and environment« less

An introduction to repast simphony modeling using a simple predator-prey example.

Abstract: Repast is a widely used, free, and open-source, agent-based modeling and simulation toolkit Three Repast platforms are currently available, each of which has the same core features but a different environment for these features Repast Simphony (Repast S) extends the Repast portfolio by offering a new approach to simulation development and execution This paper presents a model of wolf-sheep predation as an introductory tutorial and illustration of the modeling capabilities of Repast S We use a model of wolf-sheep predation to demonstrate the capabilities of the Repast S toolkit and as an introductory tutorial While the example is not intended to model real phenomenon, the model's complexity is high enough to illustrate how the user may develop multi-agent models Spatial and temporal patterns emerge in the model consisting of potentially hundreds of instances of three agent types It is important to note that Repast S and its related tools are still under development This paper presents the most current information at the time it was written However, changes may occur before the planned final release

Agent-based system for reconfiguration of distributed chemical reactor network operation

Abstract: Control of spatially distributed systems is a challenging problem because of their complex nature, nonlinearity, and generally high order. Agent-based control structures provide a powerful tool for managing distributed systems by utilizing local and global information obtained from the system. A hierarchical, agent-based system with local and global control agents is developed to control networks of interconnected chemical reactors hosting multiple autocatalytic species. The global controller agent dynamically updates the objective of local control agents as the reactor network conditions change. The case illustrated in this paper is to change the dominant species in one CSTR by modifying feed and interconnection flow rates with the constraint of shortest path possible, which causes the least amount of changes in the whole network. The agent-based system and the reactor networks are implemented using the agent-based system development framework RePast.

Legacy model integration with repast simphony.

Abstract: Repast is a widely used, free, and open-source, agent-based modeling and simulation toolkit. Three Repast version 3 platforms are currently available, each of which has the same core features but with differing environments for these features. Repast Simphony (Repast S) extends the Repast 3 portfolio by offering a new approach to simulation development and execution. Repast S's new simulation development capabilities include direct support for integrating existing (i.e., legacy) file-based models into agent-based simulations. This paper reviews related work on model integration and data exchange; introduces the Repast S's legacy model integration system; and discusses how the new system can be used to integrate existing file-based models, either agent-based or nonagent-based, into agent models.

Demeter, persephone, and the search for emergence in agent-based models.

Abstract: In Greek mythology, the earth goddess Demeter was unable to find her daughter Persephone after Persephone was abducted by Hades, the god of the underworld. Demeter is said to have embarked on a long and frustrating, but ultimately successful, search to find her daughter. Unfortunately, long and frustrating searches are not confined to Greek mythology. In modern times, agent-based modelers often face similar troubles when searching for agents that are to be to be connected to one another and when seeking appropriate target agents while defining agent behaviors. The result is a 'search for emergence' in that many emergent or potentially emergent behaviors in agent-based models of complex adaptive systems either implicitly or explicitly require search functions. This paper considers a new nested querying approach to simplifying such agent-based modeling and multi-agent simulation search problems.