Validation is the process of determining if a model adequately represents the system under study for the model's intended purpose. Validation is a critical component in building the credibility of a simulation model with its end-users. Effectively conducting validation can be a daunting task for both novice and experienced simulation developers. Further compounding the difficult task of conducting validation is that there is no universally accepted approach for assessing a simulation. These challenges are particularly relevant to the paradigm of Agent-Based Modeling and Simulation (ABMS) because of the complexity found in these models' mechanisms and in the real-world situations they attempt to represent. To aid both the novice and expert in conducting a validation process for an agent-based simulation, this article reviews nine methods that are useful for this process, including foundational topics of docking, empirical validation, sampling, and visualization, as well as advanced topics of bootstrapping, causal analysis, inverse generative social science, and role-playing. Each method is reviewed with respect to its benefits and limitations as a validation-supporting method for ABMS. Suggestions that may support a validation plan for an agent-based simulations, are also provided. This article is an introductory guide for understanding and conducting ABMS validation for developers of all experience levels.

The American scientist Carl Sagan once said: “You have to know the past to understand the present.” We argue that having a meaningful dialogue on the future of simulation requires a baseline understanding of previous discussions on its future. For this paper, we conduct a review of the discrete event simulation (DES) literature that focuses on its future to understand better the path that DES has been following, both in terms of who is using simulation and what directions they think DES should take. Our review involves a qualitative literature review of DES and a quantitative bibliometric analysis of the Modeling and Simulation (M&S) literature. The results from the bibliometric study imply that demographics of the M&S community are rapidly changing, both in terms of the nations that use M&S and the academic disciplines from which new simulationists hail. This change in demographics has the potential to help aid the community face some of its future challenges. Our qualitative literature review indicates that DES still faces some significant challenges: these include integrating human behavior; using simulation for exploration, not replication; determining return on investment; and communication issues across a splitting community.

Researchers tend to model people as individuals rather than as members of groups. This approach diminishes the impact of altruism and other group-supporting behaviors. For example, walkers may move slower than their capability to retain group cohesion. Current modeling approaches to capture group formation and dynamics lack the strategic elements required to model the complexity of human decision-making. Game theory provides a mechanism to introduce this strategic behavior. This article investigates strategic group formation through the introduction of cooperative game theory techniques into an agent-based model and simulation (ABMS). It shows some empirical results from this introduction. The approach requires looking at the Core instead of the more common Nash Equilibrium. The simulation outputs show some agents forming a large dominant group, much like a real-world mob. The model and results are relevant to policymakers trying to understand how humans navigate an environment through strategic social interactions.

A serious and imminent threat to a recovery of the global recession comes in the form of a burgeoning financial contagion known as strategic mortgage default. We theorize that the advocacy of strategic default can be likened to a disease, and as such, we employ a methodology from the field of epidemiology to measure how quickly this disease can spread throughout a society. We find that in our current fragile market, advice by influential mavens for underwater homeowners to exercise their put option could result in a flood of strategic defaults causing a contagious downward spiral of residential real estate prices. Asymmetrically, when mavens recommend that homeowners not default, their ability to save a failing market is far more limited.