Jang Won Bae

DEVSim++Toolset for Defense Modeling and Simulation and Interoperation

Discrete Event Systems Specification (DEVS) formalism supports the specification of discrete event models in a hierarchical and modular manner. Efforts have been made to develop the simulation environments for the modeling and simulation (M&S) of systems using DEVS formalism, particularly in defense M&S domains. This paper introduces the DEVSim++ toolset and its applications. The Object-Analysis Index (OAI) matrix is a tabular form of objects and analysis indices for requirements analysis. DEVSim++ is a realization of DEVS formalism in C++ for M&S. VeriTool is a DEVS model verification tool. DEVSimHLA is a library to support High-level Architecture (HLA) in DEVSim++. Other tools, including KComLib, FOM2CPPClass, and KHLAAdaptor, are used to develop a smart adaptor that allows for the interoperation of simulators of any kind. PlugSim is a distributed simulation framework using plug-in methods. These tools are utilized in every stage of the M&S development process, as well as in every application of the M&S missions to the military domain. Accordingly, the applications implemented by the toolset are used in the training, analytic, and acquisition missions of the Republic of Korea military branches. We expect the DEVS applications to become more prolific as M&S demands grow, and our toolset is already proven as complete and efficient in the domain of defense M&S.

Formal specification supporting incremental and flexible agent-based modeling

Agent-based models have been used for diverse domains such as military, sociology, and urban planning. There is a growing concern about the incrementality and the flexibility of the agent-based models in further sophisticated and large-scale utilization. To resolve this concern, we suggest that specifying agent-based models formally will resolve the problems of incrementality and flexibility of the agent-based models through an organized composition of model components. To organize the composition of agent-based models, we survey formalisms that are applicable to agent-based models, including formalisms from the discrete event models, i.e., DEVS, MDEVS, and Cell-DEVS, as well as formalisms used in the communities of agent-based models, i.e., BDI, MDP, and Game Theory. Then, we compare, contrast, and propose an overarching formal specification for agent-based models that embody the key nature of agents. As an example, we show how to incrementally merge and flexibly manage traditional agent-based models through proposed formal specifications.

Simulation-based analyses of an evacuation from a metropolis during a bombardment

The bombardment of a metropolis is considered a nightmare scenario. To reduce losses from such an assault, big cities have developed evacuation policies in case of bombardment. However, to build efficient evacuation policies, much footing data is required that considers both military and civilian views. Agent-based modeling and simulation could be utilized as a method to obtain the footing data. In this paper, we develop an evacuation agent-based model that describes a massive evacuation through the road network of a metropolis during a bombardment. In particular, our model took account of bombing strategies (i.e. the military view) as well as the characteristics of roads and evacuation agents (i.e. the civilian view) in order to analyze evacuations from both military and civilian perspectives. Moreover, we applied real data from a target region to calibrate parameters and initial conditions of the evacuation agent-based models, which increased the reliability of simulation results. Using the evacuation agent-based model, we designed and performed virtual experiments with varying military and civilian factors. Through the various analyses on the experiment results, we showed that our model could be a framework that provides footing data to develop efficient evacuation policies and preparations.

Simulation Experiment of Disaster Response Organizational Structures With Alternative Optimization Techniques

Disaster response operations are critical for decreasing the devastating impacts that result in casualties and property damages. Since these operations require cooperation in dynamic and complex situations, the responding organizations require a solid organizational structure collectively. This article introduces computational designs and evaluations of alternative organizational structures for disaster responses to resolve the disconnections between resource demands and supplies. In particular, this research consists of (1) organizational structure designs with two optimization techniques, (2) agent-based simulations that virtually replicate disaster response contexts, and (3) social network analysis to interpret the relations between the structures and the performances from the network perspectives. We applied this approach to log records of Hurricane Katrina, and our evaluations suggest that alternative organizations would improve operation outcomes, that is, increase the successful resource delivery counts and reduce a number of organizational conflicts. This computational approach could be further utilized in designing and evaluating organizations under complex and dynamic situations.

LDEF Formalism for Agent-Based Model Development

As agent-based models (ABMs) are applied to various domains, the efficiency of model development has become an important issue in its applications. The current practice is that many models are developed from scratch, while they could have been built by reusing existing models. Moreover, when models need reconfiguration, they often need to be rebuilt significantly. These problems reduce the development efficiency and ultimately damage the efficacy of ABM. This paper partially resolves the challenges of model reusability from the systems engineering approach. Specifically, we propose a formalism-based ABM development and demonstrate its potential to promote model reuses. Our formalism, named large-scale, dynamic, extensible, and flexible (LDEF) formalism, encourages the building of a larger model by the composition of modularly developed components. Also, LDEF is tailored to the ABM contexts to represent the agents action procedure and support the dynamic changes of their interactions. This paper shows that LDEF improves the model reusability in ABM development through its practical examples and theoretical discussions.

Efficient Flattening Algorithm for Hierarchical and Dynamic Structure Discrete Event Models

Discrete event models are widely used to replicate, analyze, and understand complex systems. DEVS (Discrete Event System Specification) formalism enables hierarchical modeling, so it provides an efficiency in the model development of complex models. However, the hierarchical modeling incurs prolonged simulation executions due to indirect event exchanges through the model hierarchy. Although direct event paths are applied to mitigate this overhead, the situation becomes even worse when a model changes its structures during simulation execution, called a dynamic structure model. This article suggests Coupling Relation Graph (CRG) and Strongly Coupled Component (SCC) concepts to improve hierarchical and dynamic structure DEVS simulation execution. CRG is a directed graph representing DEVS model structure, and SCC is a group of connected components in a CRG. Using CRG and SCC, this article presents (1) how to develop CRG from a DEVS model and (2) how to construct and update direct event paths with respect to dynamic structural changes. In particular, compared to the previous works, the proposed method focuses on the reduction of the updating costs for the direct event paths. Through theoretical and empirical analyses, this article shows that the proposed method significantly reduces the simulation execution time, especially when a simulation model contains lots of components and changes its model structures frequently. We expect that the proposed method would support the faster simulation executions of complex hierarchical and dynamic structure models.

Data Management and Time Synchronization in PlugSim: A DEVS-Based Framework for Interoperation of Simulations

As modern systems are increasing in complexity, modeling and simulating them are also becoming difficult. In particular, modeling and simulation (M&S) with one modeling method reveals the limitations of many simulation purposes. In order to tackle this limitation, the interoperation concept has been developed. For the interoperation of simulations, data management and time synchronization are indispensable. In this paper, we explain how the data management and time synchronization are performed in PlugSim environment. PlugSim is the DEVS-based framework for interoperation of simulations and its theoretical basis depends on the DEVS-BUS. PlugSim helps developers create an environment of interoperation of simulations. For better understanding, we provide an example and show the result of simulation in the case study.

Evaluation of Disaster Response System Using Agent-Based Model With Geospatial and Medical Details

Many disasters have occurred around the world and have caused sizable damage. A disaster, called a mass casualty incident (MCI), generates a large number of casualties that overwhelm the capacity of local medical resources, and the disaster responses to the MCI requires many interactions among the disaster responders. To evaluate the efficiency of the disaster responses against MCIs, this paper proposes an agent-based model describing the cooperations among the responders during the overall process in the disaster responses from transporting patients to their definitive care. In particular, the proposed model includes geospatial details, such as the road network and the location of hospitals around the disaster scene, and medical information, such as the distribution of medical resources and transporting units, in the region of interest to discover the key factors of the disaster response system that customized to the target region. The case study in this paper presents that the proposed approach was applied to describe a disaster response system and illustrates how the additional details are utilized to analyze the disaster response system. We expect that the proposed method can provide comprehensive insights to a disaster response system of interest, and it can be used as groundwork for improving the disaster response system.

Accelerated simulation of hierarchical military operations with tabulation technique

Recently, a challenge in defence modelling and simulation is that simulating a satisfactory number of scenarios often requires an infeasible runtime. This paper resolves this challenge by utilizing a tabulation technique that encourages reuses of the previous simulation results in hierarchical models. For example, a mission-level model may contain a number of similar engagement scenarios that must be executed multiple times by an engagement-level model. Therefore, we collapse the multiple similar executions into a single simulation run while verifying the statistical stability in the output distribution. This reuse is supported by adapting the tabulation technique to hierarchical models with the extension of an interpolation in matching the lower abstractions. An application in the naval air defence domain shows that the simulation is speeded up a maximum of seven times, while producing statistically identical simulation results with few increments in the variance.

Modeling Combat Entity with POMDP and DEVS

Agency for Defense DevelopmentCombat Modeling and Simulation (M&S) is significant to decision makers who predict the next direction of wars. Classical methodologies for combat M&S aimed to describe the exact behaviors of combat entities from military doctrines, yet they had a limitation of describing reasonable behaviors of combat entities that did not appear in the doctrines. Hence, this paper proposed a synthesizing modeling methodology for combat entity models considering both 1) the exact behaviors using descriptive modeling and 2) the reasonable behaviors using prescriptive modeling. With the proposed methodology, combat entities can represent a reality for combat actions rather than the classical methodologies. Moreover, the experiment results using the proposed metho-dology were significantly different from the results using the classical methodologies. Through the analyses of the experiment results, we showed that the reasonable behaviors of combat entities, which are not specified in the doctrines, should be considered in combat M&S.