• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.3
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• pp.79-99
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• 1992

The DEVS (Discrete Event system Specification) formal model for discrete event simulation is a hierarchical, modular model. Because the DEVS formal model has a mathematical structure, it provides a theoretic background of discrete event simulation model. However, the DEVS formal model is difficult to understand because of its mathematical structure. Also, since the DEVS formal model is often constructed by heuristic, subjective method of model designer from the model, a systematic model built-in methodology does not exist. In this paper, we propose the model formalization methodology from an informal model to the DEVS formal model. For this formalization methodology, we introduce formal tools for model construction based on the DEVS ( from an informal model : Event Dependency Graph (EDG) for the event analysis and State Representation Graph(SRG) for the system state analysis.

• Journal of the Korea Society for Simulation
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• v.15 no.2
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• pp.1-12
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• 2006

As the needs of intelligent systems increase, there have been diverse approaches that combine artificial intelligence (AI) and simulation in the last decade. RG-DEVS, which is the basis for this paper, embedded AI planning techniques into the simulation modeling methodology of DEVS, in order to specify dynamically a simulation model. However, a hierarchy concept, which is used for various types of problem solving systems. is not included in the planning of RG-DEVS. The hierarchy concept reduces the computational cost of planning by reducing the search space, and also makes it easy to apply the hierarchical process flow of a target system to planning. This paper proposes Hierarchical RG-DEVS (HRG-DEVS) in an attempt to insert hierarchical planning capability into RG-DEVS. For the verification of the proposed modeling methodology, HRG-DEVS is applied to model the block's world problem of ABSTRIPS, which is a classical planning problem.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.1029-1036
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• 2007

State explosion is a well-known problem that impedes analysis md testing of discrete event systems, thus making the verification of large systems intrinsically difficult job. This paper suggests a hierarchical verification methodology of untimed DEVS model which can alleviate the state explosion problem. The method is a repetitive procedure of designing and verifying between the upper level and the lower level models abstracting away the unnecessary information with respect to a given verification task. A small example was employed to show our suggested method in detail.

• Journal of the Korea Society for Simulation
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• v.8 no.4
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• pp.109-124
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• 1999

The major objective of this research is to design and build the variable structure DEVS modeling & simulation framework. To do this, we have proposed the direct message passing mechanism between the model and its simulator to deal with the structural demand from the model during the simulation. In this approach, four types of basic messages are introduced for the vertical(creation/deletion of the child) and horizontal(creation/deletion of the brother) structural changes. Proposed methodology has been successfully applied to the multi-processor system and the forest fire information system.

• Journal of the Korea Society for Simulation
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• v.9 no.1
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• pp.39-54
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• 2000

Presented in this paper is a modeling and simulation methodology for 3 dimensional man-made systems. Based on DEVS(discrete event system specification) formalism[13], we propose GK-DEVS (geometrical and kinematic DEVS) formalism to describe the geometrical and kinematic structure and continuous state dynamics. To represent geometry and kinematics, we add a hierarchical structure to the conventional atomic model. In addition, we employ the "empty event" and its external event function for continuous state changing. In terms of abstract simulation algorithm[13], the simulation method of GK-DEVS, named GK-Simulator, is proposed for combined discrete-continuous simulation. Using GK-DEVS, the simulation of an FMS(flexible manufacturing system) consisting of a luring machine, a 3-axis machine and a RGV-mounted robot has been peformed.en peformed.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.11a
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• pp.85-89
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• 2002

Development of distributed simulation environment must be required in order to simulate the distributed models regionally and inter-operate with running simulations individually, Simulation based on DEVS formalism is difficult to simulate the distributed models. DEVS formalism is modeling methodology. To specify model, this formalism separates behavior and structure, therefore it is able to design complex model easily. HLA is standard framework of distribute simulation environment, It is defined to facilitate the interoperability and the reusability. RTI (Run Time Infrastructure) is software that provides common service to simulation systems and implementation of the HLA Interface Specification. Method of implementation is that modules cooperating with RTI are added to simulator on DEVS simulation environment. On the DEVS simulation environment (DEVS-Obj -C) that already developed, Highest class of abstract simulator uses service that RTI provide, then This environment is able to change DEVS model into Federate and run distribute simulation that inter-operates with the RTI. Because this distributed simulation environment includes convenience of modeling that obtains through the DEVS formalism and accompanies HLA standard, this environment make it possible to simulate with_ complex systems and heterogeneous simulations

• Journal of the Korea Society of Computer and Information
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• v.23 no.2
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• pp.45-51
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• 2018

In this paper, we propose a Designed and Developed home router management system. Through the fourth industrial revolution and development of IoT technology, now people can experience a wide range of IoT related services at their workplace or daily lives. At the industrial site, IoT devices are used to improve productivity such as factory automation, and at home, IoT technology is used to control home appliances from a remote distance. Usually IoT device is integrated and controlled by the router. Home router connects different IoT devices together at home, however when security issues arise, it can invade personal privacy. Even though these threats exist, the perception for home router security is still insufficient. In this paper, we have designed and developed home router management system using DEVS methodology to promote the safe use of home router. Through the DEVS methodology, we have designed the system and developed the mobile application. This management system enables users to set up security options for home router easily.

• Proceedings of the Korea Society for Simulation Conference
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• 2002.05a
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• pp.253-258
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• 2002

This paper proposes a methodology for development of protocol models. The methodology attempts to employ two modeling environments in models development, NS2 and DEVSim++, which will interoperate during simulation. NS2 is a widely used network simulator in protocol research, which employs an informal modeling approach. Within the approach time and state information of protocol models are not explicitly described, thus being hard to validate model. On the other hand the DEVS formalism is a mathematical framework for modeling a discrete event system in a hierarchical, modular manner. In DEVS, model's time and state information is described explicitly, By using DEVS formalism, models can easily be validated and errors in the modeling stage can be reduced. However, the DEVS simulator, DEVSim++, supports a small amount of models library which are required to build simulation models of general communication network. Although NS2 employs an informal modeling approach and models validation is difficult, it supports abundant models library validated by experimental users. Thus, combination of DEVS models and NS2 models may be an effective solution for network modeling. Such combination requires interoperation between DEVSim++ simulator and NS2 simulator. This paper develops an environment for such interoperation. Correctness and effectiveness of the implemented interoperation environment have been validated by simulation of UDP and TCP models.

• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.127-136
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• 2009

Modeling and Simulation, especially in mobile ad hoc network(MANET), are the most effective way to analyze performance or optimize system parameters without establishing real network environment. Focusing mainly on overall network behaviors in MANET concerns dynamics of network transport operations, which can efficiently be characterized with event based system states rather than execution details of protocols. We thus consider the network as a discrete event system to analyze dynamics of network transport performance. Zeigler's set-theoretic DEVS(Discrete Event Systems Specification) formalism can support specification of a discrete event system in hierarchical, modular manner. The DEVSim++ simulation environment can not only provide a rigorous modeling methodology based on the DEVS formalism but also support modelers to develop discrete event models using the hierarchical composition methodology in object-orientation. This environment however hardly supports to specify connection paths of network nodes, which are continuously altered due to mobility of nodes. This paper proposes a DEVS-based modeling and simulation methodology of enabling node mobility, and develops DEVS models for the mobile ad hoc network. We also simulate developed models with the DEVSim++ engine to verify the proposal.

• Journal of the Korea Society for Simulation
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• v.5 no.2
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• pp.41-58
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• 1996

The Discrete Event Systems Specification(DEVS) formalism specifies a discrete event system in a hierarchical, modular form. This paper presents a distributed simulation environment D-DEVSim++ for models specified by the DEVS formalism. D-DEVSim++ employs a new simulation scheme which is a hybrid algorithm of the hierarchical simulation and Time Warp mechanisms. The scheme can utilize both the hierarchical scheduling parallelism and the inherent parallelism of DEVS models. This hierarchical scheduling parallelism is investigated through analysis. Performance of the proposed methodology is evaluated through benchmark simulation on a 5-dimensional hypercube parallel machine. The performance results indicate that the methodology can achieve significant speedup. Also, it is shown that the analyzed speedup for the hierarchical scheduling time corresponds the experiment.