Activity-based simulation using DEVS: increasing performance by an activity model in parallel DEVS simulation

Improving simulation performance using activity tracking has attracted attention in the modeling field in recent years. The reference to activity has been successfully used to predict and promote the simulation performance. Tracking activity, how- ever, uses only the inherent performance information contained in the models. To extend activity prediction in modeling, we propose the activity enhanced modeling with an activity meta-model at the meta-level. The meta-model provides a set of interfaces to model activity in a specific domain. The activity model transformation in subsequence is devised to deal with the simulation difference due to the heterogeneous activity model. Finally, the resource-aware simulation framework is implemented to integrate the activity models in activity-based simulation. The case study shows the improvement brought on by activity-based simulation using discrete event system specification （DEVS）.     

Multi-resolution modeling based on quotient space and DEVS

As simulation systems get more and more complex, the study of multi-resolution modeling (MRM) remains an exciting and fertile area of research. Contrasting its abundant successful use cases, a rigorous mathematical foundation is still lacking in MRM. In this paper, we propose a quotient space based multi-resolution modeling (QMRM) theory based on granular computing in artificial intelligence and on discrete-event system specification (DEVS) in modeling and simulation. Based on quotient sets, resolution, multi-resolution modeling and other related concepts are defined and a general concept framework is constructed. Based on the concepts of quotient set and natural projection, several MRM principles are derived. The internal consistency principle guarantees consistency among different perspectives of an atomic model, whereas the external consistency principle guarantees that different components in a coupled model are consistent. The false-preserving principle indicates that if a construction relation or state transformation relation of a component does not exist in a low resolution model, then the corresponding relations should not exist in its high resolution model. The true-preserving principle tells us that a high resolution model can be simplified by choosing the proper low resolution model. QMRM is not only a formal specification, but also a fundamental framework to understand MRM concepts, a guiding ideology to design specific MRM methods, and a modeling methodology to develop MRM systems. QMRM is created from a general simulation perspective, not limited by any specific application or problem domain aspects. The results of this paper can serve as a starting point for further study of multi-resolution problems in different domains.     

DEVS modeling of mobile wireless ad hoc networks

Ad hoc networks are self-organizing wireless systems conformed by cooperating neighboring nodes that conform networks with variable topology. Analyzing these networks is a complex task due to their dynamic and irregular nature. Cellular Automata (CA), a very popular technique to study self-organizing systems, can be used to model and simulate ad hoc networks, as the modeling technique resembles the system being modeled. Cell-DEVS was proposed as an extension to CA in which each cell in the system is considered as a DEVS model. The approach permits defining models with asynchronous behavior, and to execute them with high efficiency. We show how these techniques can be used to model mobile wireless ad hoc networks, making easy model definition, analysis and visualization of the results. The use of Cell-DEVS permitted us to easily develop new experiments, which allowed us to extend routing techniques for inter-networking and multicast routing, while permitting seamless integration with traditional networking models.     

Activity-based OO business modeling and control

The paper considers how process modeling can help you control or assess the impact of changes to a software process. It discusses business modeling for control, change management, object oriented business modeling and an industry case study     

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.     

DEVSpecL: DEVS specification language for modeling,simulation and analysis of discrete event systems

Discrete EVent Systems Specification (DEVS) formalism supports specification of discrete event models in a hierarchical modular manner. This paper proposes a DEVS modeling language called DEVS Specification Language (DEVSpecL) based on which discrete event systems are modeled, simulated and analyzed within a DEVS-based framework for seamless systems design. Models specified in DEVSpecL can be translated in different forms of codes by code generators, which are executed with various tools for models verification, logical analysis, performance evaluation, and others.     

Activity-based design

In many types of activities, communicative and material activities are so intertwined that the one cannot be understood without taking the other into account. This is true of maritime and hospital work that are used as examples in the paper. The spatial context of the activity is also important: what you can do depends upon where you are. Finally, human and automatic machinery alternate in filling certain roles in the activity: sometime the officer maintains the course, sometimes the autopilot. Such activities require us to rethink the traditional oppositions between communication and instrumental actions, between human and non-human participants, and between an activity and its spatio-temporal context. The advent of pervasive technologies, where active or passive systems become embedded in our working and living spaces, from where they offer their services to us, puts the need to reconsider these basic oppositions high on the research agenda. This paper presents a consistent framework called habitats for understanding communicative and material activities and their interplay, for understanding how activities can be associated to physical surroundings, and for understanding how humans and automatic machinery can replace one another in an activity. It also gives an example of how to use the framework for design.     

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。     

基于DEVS的交叉路口建模与仿真

考虑有信号控制的交叉路口内车辆之间、车辆与行人之间的冲突，在离散事件仿真规范（DEVS）框架下构建了交叉路口微观交通仿真模型.以某市典型交叉路口观察数据标定仿真参数，将仿真结果与按《城市道路设计规范》计算得到的通行能力进行比较，验证了模型.在此基础上，首先，仿真分析了不同左转比例对交叉路口通行能力的影响；然后，基于各方向等待通过交叉路口的车辆数目设计了智能绿信比控制策略.仿真试验表明：通行能力随着左转车比例的增加先上升后下降；智能绿信比控制能显著提升交叉路口通行能力，明显降低平均引道延误时间.由此证明仿真模型能真实地模拟交叉路口各因素间的相互作用，且易于扩充，通用性强，能够用于其它智能交通问题的研究.     

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。     

用MATLAB对离散事件系统进行仿真

文章着重讨论用ＭＡＴＬＡＢ对离散事件系统进行仿真时的一些关键技术,如随机数发生器的生成、出入队列处理、换队处理等,并以排队系统为例进行仿真实验,以说明用ＭＡＴＬＡＢ对离散事件系统仿真的方便性和有效性。     

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。     

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.      

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.     

A location-based fog computing optimization of energy management in smart buildings: DEVS modeling and design of connected objects

Nowadays, smart buildings rely on Internet of things (IoT) technology derived from the cloud and fog computing paradigms to coordinate and collaborate between connected objects. Fog is characterized by low latency with a wider spread and geographically distributed nodes to support mobility, real-time interaction, and location-based services. To provide optimum quality of user life in modern buildings, we rely on a holistic Framework, designed in a way that decreases latency and improves energy saving and services efficiency with different capabilities. Discrete EVent system Specification (DEVS) is a formalism used to describe simulation models in a modular way. In this work, the sub-models of connected objects in the building are accurately and independently designed, and after installing them together, we easily get an integrated model which is subject to the fog computing Framework. Simulation results show that this new approach significantly, improves energy efficiency of buildings and reduces latency. Additionally, with DEVS, we can easily add or remove sub-models to or from the overall model, allowing us to continually improve our designs.     

Extending the DEVS formalism for massively parallel simulation

The use of multiprocessors for discrete event simulation is an active research area where work has focused on strategies for model execution with little regard for the underlying formalism in which models may be expressed. However, a formalism-based approach offers several advantages including the ability to migrate models from sequential to parallel platforms and the ability to calibrate simulation architectures to model structural properties. In this article, we extend the DEVS (discrete event system specification) formalism, originally developed for sequential simulation, to accommodate the full potential of parallel processing. The extension facilitates exploitation of both internal and external event parallelism manifested in hierarchical, modular DEVS models. After developing a mapping of the extended formalism to parallel architectures, we describe an implementation of the approach on a massively parallel architecture, the Connection Machine. Execution results are discussed for a class of models exhibiting high external and internal event parallelism, the so-called broadcast models. These verify the tenets of the underlying theory and demonstrate that significant reduction in execution time is possible compared to the same model executed in serial simulation.     

DEVS formalism: a framework for hierarchical model development

A methodology is being developed to map hierarchical, modular discrete event models onto distributed simulator architectures. Concept developed for the first step of the methodology concerning model representation are discussed. The DEVS (Discrete Event System Specification) is extended to facilitate modular, hierarchical model specification. Procedures for top-down model development are expressed with the extended formalism and illustrated with a computer system model design     

Adaptive Queueing: A Study Using Dynamic Structure DEVS

Conventional modeling methodologies only give support for the representation of model behavior, providing no help for describing changes in model structure. Some models are better represented by changes in their structure. Instead of forcing these changes to be represented at the simple behavioral level, a strong theoretical support is needed to allow the representation of structural changes in a natural way. In this paper we present a new modeling methodology for representing Dynamic Structure Systems. To illustrate this methodology we describe a dynamic structure queueing system. This system dynamically changes its structure to improve performance.     

DEVS methodology for evaluating time-constrained message routing policies

Due to its ability to support temporal issues of systems, discrete event simulation is widely applicable to real-time system design. This paper presents a methodology for the modeling and simulation of time-constrained message routing policies for hypercube interconnected real-time systems. The methodology is based on a framework called the DEVS (discrete event systems specification) formalism which supports modular and hierarchical specification of discrete event models. Within the methodology, we first develop DEVS specification for models for hypercube computers and experimental frames to measure the performance of alternative message routing policies. We then implement such specification in DEVSIM++, a C++-based modeling/simulation environment that implements the DEVS formalism. Simulations of various message routing policies are performed, and the performances of such policies are compared.