DEVS的面向对象可视化建模

DEVS是对离散事件系统的一种形式化描述,该文在DEVS中引入面向对象的方法,并采用UML（Unified Modeling Language)对它进行可视化建模。文中提出了基于DEVS的面向对象的一种建模规则和基于UML的可视化建模思想和方法,该方法是对DEVS和UML的扩充和改进。     

基于DEVS/CD++的抢险救灾物资保障仿真建模研究

突发自然灾害条件下的抢险救灾行动是典型的离散事件系统,在分析离散事件系统规范(DEVS)模型描述的基础上,构建了抢险救灾物资保障DEVS仿真模型,分析了仿真实体,设计了仿真流程,给出了耦合模型和主要原子模型结构。并在CD++中对该模型进行了仿真试验,得到了较为合理的仿真结果,为开展抢险救灾应急保障模拟训练奠定了基础。     

一种DEVS原子模型向UML状态图映射方法研究

离散事件仿真规范DEVS形式化的一个重要不足在于它缺乏一种标准的、图形化的描述形式。该文研究提出了一种将DEVS的原子模型与复合模型分别映射到UML的状态图和组件图的方法,并用形式化的数学方法对DEVS原子模型向UML状态图的映射过程进行了描述与构造。这种映射将DEVS规范融入到了UML的描述形式当中,将DEVS的抽象化描述与UML的表示能力、计算机处理能力结合起来,为两种建模形式的统一提供了一个可行的思路。该文研究的成果在C^4ISR系统总体方案规范化建模中得到了逐步的应用。     

一种基于Modelica语言的混合系统DEVS模型架构

Modelica语言采用微分方程描述系统,此外它还具备面向对象编程语言的特性,因此它不仅适用于连续系统的建模,还支持离散系统的模型架构。因此,可以将Modelica作为一种混合系统的建模语言。提出了一个Modelica语言描述的DEVS（Discrete E Vent System specification离散事件系统规范）模型架构,并通过对模型的编译过程产生C＋＋代码,获取了同时描述连续系统和离散系统建模的能力。最后给出了用Modelica语言描述的一个飞机导航控制连续一离散仿真系统的例子。     

基于SystemC的航电系统故障建模仿真方法

面向民用航空维修训练领域,提出一种模块化、层次化的故障行为建模仿真方法。针对航电系统结构复杂、故障种类繁多、信息流难以控制等特点,依据飞机相关手册资料,采用离散事件系统DEVS(Discrete Event System)描述系统的结构和行为,采用电气线性网络ELN(Electrical Linear Networks)计算模型描述系统的电气特性,在System C/System C AMS仿真环境下对系统进行故障仿真。经验证该方法能真实反映正常和故障情况下航电系统电气特性和功能行为,基本满足维修训练仿真要求。     

UML-BD在C3I系统中的应用

DEVS是对离散事件系统的一种形式化描述,它提供了一种层次的模块化的系统说明方法。该文中的UML-BD（UML Based on DEVS）方法就是在UML中结合DEVS这一特点,对UML进行一定的扩展;同时还在UML中还增加了时间的约束．满足系统的实时性的要求。基于C3I系统的层次性、实时性的特点,该文采用UML-BD方法对系统进行建模,构建出系统模型能够充分地展现系统特点。     

基于逻辑模型的自动化制造系统建模方法

系统调适是自动化制造系统在实际应用前的重要阶段，但是传统的系统调适存在周期长、成本高等问题。虚拟调适可以有效解决这些问题，在本次研究中提出采用离散事件系统规范(Discrete Event System Specification, DEVS)来构建虚拟调适系统中的逻辑模型，并对其进行了扩展和改进。同时利用DEVS++进行二次开发和仿真分析，重复验证建立的逻辑模型并进行修改。在结果的实例分析中，以自动化制造系统为例，对逻辑模型的建立进行了展示。同时该模型的召回率为91%,准确率为86%,F值为79%;其准确率相较于灰狼算法和文献方法分别提高了6.25%和14.86%。结果证实了实验中提出的基于逻辑模型的系统建模方法具有可行性和优越性，对于自动化制造系统的模型构建具有较好的技术参考价值。     

DEVS在IDEF0模型验证中的应用

IDEF0方法是结构化系统分析的重要方法,但IDEF0模型是静态的功能模型,不包含运行机制,不便于进行动态分析,导致对模型的验证较为困难.本文建立了IDEF0模型的形式化描述,并对IDEF0模型进行了扩展,提出IDEF0模型到离散事件系统规范(DEVS)模型的转化方法,通过DEVS的仿真运行来对IDEF0模型进行分析和验证.该方法实现了IDEF0方法中系统分析与模型验证的有效衔接,具有扩展性和灵活性,为IDEF0模型的验证提供了支持.     

离散信号事件驱动的自动测试系统仿真验证方法与实现

为在设计早期对复杂自动测试系统进行充分验证从而加速其成熟并降低研发成本,对离散事件系统规范进行扩展和改进,在原子模型中引入了端口和故障模式,通过端口间的连接构成耦合模型,提出一种离散信号事件驱动的仿真调度算法,并给出一个C/S架构的支持远程交互的仿真验证实现方案;基于自研的SCATS自动测试系统软件平台,分别针对一个示例系统和真实系统开展了实验,结果表明所提模型和方法支持复杂系统多分辨率层次化建模,仿真具有较高的一致性和执行效率,满足自动测试系统仿真验证工程应用需求。     

支持模型集成和重用的仿真语言研究

SRML是一种基于XML和脚本语言，用于表示仿真模型的参考标记语言。它试图确定一个灵活的表示仿真模型的参考标准，以加快模型的开发速度，支持模型的集成和重用，但是其草案大纲存在很多不足，需要进行扩展完善。总结了仿真模型集成和重用的关键因素，并提出结合DEVS、DEVS定义语言，研究扩展SRML的途径。重点介绍了DEVS和SRML之间的映射关系，以及SRML用于描述仿真模型的能力，如数据交互格式、继承关系、原子模型、组合模型、交互关系、仿真想定的描述等。扩展的SRML实现了仿真模型与仿真执行的分离，并继承了DEVS的所有特性，是一种平台无关的仿真语言，可以有效地支持仿真模型的集成和重用。     

REALIZATION THEORY OF DISCRETE-EVENT SYSTEMS AND ITS APPLICATION TO THE UNIQUENESS AND UNIVERSALITY OF DEVS FORMALISM

Many man-made systems have discrete event nature. Many modeling formalisms for discrete-event mechanisms have invented and been used for many problems. Among those models, the DEVS formalism is to provide natural and universal models in some sense.

This paper first provides a realization theory of general discrete-event systems. That is, a behavioral definition of discrete-event system is defined, and then a state transition function of the system is constructed. Based on the realization, the uniqueness problem of representations for discrete-event systems is positively solved. Furthermore, as an application of that solution, this paper shows both the fact that a legitimate DEVS with surjective internal transition function is unique up to isomorphism in the class of state representations of the state system defined from the DEVS, and the fact that any discrete-event system has a DEVS realization. In this sense the DEVS modeling facility has the uniqueness and universality in modeling discrete event mechanisms.     

Maneuvering control simulation of underwater vehicle based on combined discrete-event and discrete-time modeling

When designing or acquiring underwater vehicles such as submarines and torpedoes, it is necessary to predict their performance precisely and perform tests repeatedly using modeling and simulation at both the engineering level and the tactical engagement level. For simulation performed for analysis purposes at the engineering level, which requires a considerable amount of computation power, a discrete-time system simulation that computes significant values at every single unit time using the established mathematical model or engineering model is mainly employed. To simulate a complex or complicated task such as a traffic analysis or tactical measure of effectiveness (MOE) analysis at the engagement level, it is appropriate to use a discrete-event system simulation that causes transition between model states through the triggering of events on the basis of the passing of messages between simplified mathematical models coupled in various ways. In this paper, we studied a maneuvering control of underwater vehicle from the perspective of a combined discrete-event and discrete-time system simulation; the simulation model is established on the basis of discrete-event system specification (DEVS) formalism, which is a representative modeling formalism of a discrete-event system simulation. In detail, the simulation includes DEVS modeling implementations of simulation execution time control and discrete-time step size control in real time at the time of performing a discrete-time system simulation for the purpose of three-dimensional visualization or carrying out a performance analysis using the DEVS model. This hybrid approach makes possible to build a simulation-based expert system which supports the decision making for the acquisition of an underwater vehicle.     

Self-reproducible DEVS formalism

System reproduction model to the growing system structure can be used to design modeling formalisms for variable system architectures having historical characteristics. We introduce a discrete event system specifications (DEVS)-based extended formalism that a system structure gradually grows through self-reproductions of system components. The proposed formalism is applied to atomic DEVS modeling and coupled DEVS modeling. As extended-atomic DEVS model, atomic self-reproduction (SR) DEVS modeling to a system component makes virtual-child atomic DEVS models. By SR DEVS modeling, a child coupled model can be also reproduced from a parent coupled model. When a system component model reproduces its system component, a child component model can receive its parent model characteristics including determined role or behavior, and include different structure model characteristics. A virtual-child model that has its parent characteristics can also reproduce next child model which may show similar attributes of the grand-parent model.     

Reachability Graph of Finite and Deterministic DEVS Networks

This paper shows how to generate a finite-vertex graph, called a reachability graph for discrete-event system specification (DEVS) network. The reachability graph is isomorphic to a given original DEVS network in terms of behavior but the number of vertices as well as the number of edges of the reachability graph are finite.      

Discrete-event modelling of fire spreading

We deal here with the application of discrete-event System Specification (DEVS) formalism to implement a semi-physical fire spread model. Currently, models from physics finely representing forest fires are not efficient and still under development. If current softwares are devoted to the simulation of simple models of fire spread, nowadays there is no environment allowing us to model and simulate complex physical models of fire spread. Simulation models of such a type of models require being easily designed, modified and efficient in terms of execution time. DEVS formalism can be used to deal with these problems. This formalism enables the association of object-oriented hierarchical modelling with discrete-event techniques. Object-oriented hierarchical programming facilitates construction, maintenance and reusability of the simulation model. Discrete-events reduce the calculation domain to the active cells of the propagation domain (the heated ones).     

Hybrid system modeling using the SIMANLib and ARENALib Modelica libraries

The ARENALib and SIMANLib Modelica libraries replicate the basic functionality of the Arena simulation environment and the SIMAN language. These libraries facilitate describing discrete-event models using the Arena modeling methodology. ARENALib and SIMANLib models can be combined with other Modelica models in order to describe complex hybrid systems (i.e., combined continuous-time and discrete-event systems). The implementation and design of SIMANLib and ARENALib is discussed. The ARENALib components have been built in a modular fashion using SIMANLib. The SIMANLib components have been described as Parallel DEVS models and implemented using DEVSLib, a Modelica library previously developed by the authors to support the Parallel DEVS formalism. The use of Parallel DEVS as underlying mathematical formalism has facilitated the development and maintenance of SIMANLib. The modeling of two hybrid systems is discussed to illustrate the features and use of SIMANLib and ARENALib: firstly, a soaking-pit furnace; secondly, the malaria spread and an emergency hospital. DEVSLib, SIMANLib and ARENALib can be freely downloaded from http://www.euclides.dia.uned.es/.     

Object-oriented business process modeling and simulation:: A discrete event system specification framework

In this study, we suggest that the Discrete Event System Specification (DEVS) framework, derived from engineering research, provides a useful Object-Oriented Modeling and Simulation (OOMS) approach for developing, simulating and evaluating complex business process models. A survey of other OOMS approaches to business process modeling, and their evaluation with regard to model representation, manipulation and implementation, suggests that there are some limitations which could be addressed by DEVS. We conducted a case study of a business process in a “real world” setting to explore some of the issues involved in implementing the DEVS framework.Our findings suggest that DEVS provides a robust framework for model representation based on its concept of atomic models and its ability to represent higher-level models that are closed under coupling. It also provides considerable model manipulation capabilities through a System Entity Structure (SES), the pruning of the SES by inclusion of instances of models which correspond to processing alternatives, and a relatively easy transition from conceptual models to simulation models. Finally, our implementation of DEVS in a business situation contributes to the parent discipline by highlighting a number of methodological issues such as discrepancy resolution by identifying root causes, assumptions surfacing and re-examination, and an awareness of the political and cultural context of business process modeling. Our study suggests that IS research on developing OOMS approaches to business process modeling can derive considerable benefits by leveraging off DEVS-related research in engineering.     

A new cell space DEVS specification: Reviewing the parallel DEVS formalism seeking fast cell space simulations

This paper introduces a new specification for cellular DEVS models that assures high performance. It starts with the parallel DEVS specification and derives a high performance cellular DEVS layer using the property of closure under coupling. This is done through converting the parallel DEVS into its equivalent non-modular form which involves computational and communication overhead tradeoffs. The new specification layer, in contrast to multi-component DEVS, is identical to the modular parallel DEVS in the sense of state trajectories which are updated according to the modular message passing methodology. The equivalency of the two forms is verified using simulation methods. Once the equivalency has been ensured, analysis of the models becomes a decisive factor in employing modularity in cellular DEVS models. Non-modular models guarantee the efficiency of the models in contrast to the current cellular DEVS implementation approaches. This was achieved by converting the cell space partially or fully into atomic model in order to eliminate inter-cell messages. However, the new specification needs an automated way to implement and verify models since they might become complicated ones.     

Knowledge-based environment for investigating multicomputer architectures

Multicomputers for massively parallel processing will eventually employ billions of processing elements, each of which will be capable of communicating with every other processing element. A knowledge-based modelling and simulation environment (KBMSE) for investigating such multicomputer architecture at a discrete-event system level is described. The KBMSE implements the discrete-event system specification (DEVS) formalism in an object-oriented programming system of Scheme (a dialect), which supports building models in a hierarchical, modular manner, a systems-oriented approach not possible in conventional simulation languages. The paper presents a framework for knowledge-based modelling and simulation by exemplifying modelling a hypercube multicomputer architecture in the KBMSE. The KBMSE has been tested on a variety of domains characterized by complex, hierarchical structures such as advanced multicomputer architectures, local area computer networks, intelligent multi-robot organizations, and biologically based life-support systems.