Event System Specification Formalism Research Articles

Discrete Event Simulation-Based Reliability Evaluation of a Traffic Signal Controller

A mission reliability evaluation methodology for a signal traffic controller is presented in this paper. To develop the new evaluation methodology, this paper combines the Discrete Event System Specification (DEVS) formalism which has been popular in manufacturing area for three reasons: (1) its features compatible with the object-oriented modeling; (2) its rigorous formal definition; and (3) its support for the specifications of discrete event models in a hierarchical and modular manner. By using the DEVS formalism, we construct a simulation model which takes into account not only the characteristics of a traffic signal controller but also the operating environment. Once a model is constructed, it is possible to perform simulation experiments. The proposed methodology computes the mission reliability of a traffic signal controller by using a simulation record, and this information plays a vital role in preparing optimized maintenance policies that maximize availability or minimize life cycle costs.

Practical aspects of the DesignDEVS simulation environment

DesignDEVS is a simulation development environment based on the Discrete Event System Specification (DEVS) formalism. This paper provides an in-depth overview of the software while focusing on the practical considerations influencing its design. Practitioners who stand to benefit from systems engineering will approach formalism-based simulation tools with little knowledge of the underlying theory. It is therefore important that theoretical principles, such as the separation of model and simulator, be emphasized by the user interface. Other practical aspects of DesignDEVS include the simplicity of atomic model code, a focus on coupling for collaboration purposes, the enforcement of essential modeling constraints, and a reliance on best practices in cases where strict enforcement might inconvenience users. In DesignDEVS, an issue we refer to as the Insidious Pointer Problem is aggressively tackled through run-time error handling. By contrast, the separation of output values from state transitions is left as a best practice for the sake of user convenience. The design decisions explained in this paper are relevant to developers of other formalism-based tools seeking widespread adoption of scalable modeling and simulation practices.

Combining DEVS and model-checking: concepts and tools for integrating simulation and analysis

Our objectives here are to discuss the development of a formal framework that exploits the advantages of the discrete event system specification (DEVS) formalism and builds upon recent extensive work on verification combining DEVS and model checking for hybrid systems. DEVS offers the ability, via mathematical transformations called system morphisms, to map a system expressed in a formalism suitable for analysis (e.g., timed automata or hybrid automata) into the DEVS formalism for the purpose of simulation. We discuss a probabilistic extension of the FD-DEVS formalism that enables a set of model classes and tools derived from Markov-type models. The MS4 modelling environment provides a suite of tools that support this extension, called FP-DEVS. In this paper, we describe these tools and the concepts underlying them. We also provide examples of application of these concepts and discuss the open opportunities for research in this direction.

Emergence at the Fundamental Systems Level: Existence Conditions for Iterative Specifications

Conditions under which compositions of component systems form a well-defined system-of-systems are here formulated at a fundamental level. Statement of what defines a well-defined composition and sufficient conditions guaranteeing such a result offers insight into exemplars that can be found in special cases such as differential equation and discrete event systems. For any given global state of a composition, two requirements can be stated informally as: (1) the system can leave this state, i.e., there is at least one trajectory defined that starts from the state; and (2) the trajectory evolves over time without getting stuck at a point in time. Considered for every global state, these conditions determine whether the resultant is a well-defined system and, if so, whether it is non-deterministic or deterministic. We formulate these questions within the framework of iterative specifications for mathematical system models that are shown to be behaviorally equivalent to the Discrete Event System Specification (DEVS) formalism. This formalization supports definitions and proofs of the afore-mentioned conditions. Implications are drawn at the fundamental level of existence where the emergence of a system from an assemblage of components can be characterized. We focus on systems with feedback coupling where existence and uniqueness of solutions is problematic.

Event-based scenario manager for multibody dynamics simulation of heavy load lifting operations in shipyards

This paper suggests an event-based scenario manager capable of creating and editing a scenario for shipbuilding process simulation based on multibody dynamics. To configure various situation in shipyards and easily connect with multibody dynamics, the proposed method has two main concepts: an Actor and an Action List. The Actor represents the anatomic unit of action in the multibody dynamics and can be connected to a specific component of the dynamics kernel such as the body and joint. The user can make a scenario up by combining the actors. The Action List contains information for arranging and executing the actors. Since the shipbuilding process is a kind of event-based sequence, all simulation models were configured using Discrete EVent System Specification (DEVS) formalism. The proposed method was applied to simulations of various operations in shipyards such as lifting and erection of a block and heavy load lifting operation using multiple cranes.

Construction of Concurrent Programs Based on a Modeling and Simulation Formalism

This paper proposes a framework for developing a concurrent program using the discrete event system specification (DEVS) formalism. Within the proposed framework, a concurrent program is modeled by the DEVS formalism, and the modeling result is validated through simulation in a DEVS abstract simulator environment, called DEVSim++. Then, the validated modeling results are translated to multi-threaded program codes written in a conventional programming language. For that, each DEVS model which specifies behavior of a component is converted to a single thread, called an atomic thread, and every connection information between the components are clustered together and converted to a data structure, called a port mapping table. This paper also proposes an efficient solution which combines several atomic threads into a new thread, called a combined thread.

Data Upload in LTE-A Mobile Networks by Using Shared Segmented Upload

There have been ongoing efforts focused on improving mobile networks standards to support the ever-increasing user demands of high data rate services. These efforts are more crucial for cell-edge users where their long distance from their serving Base Station (BS), and the higher interference from the neighbouring cells, degrades their performance. Contemporary communication standards, proposed for Fourth Generation (4G) of mobile telecommunication standards, use different techniques to deal with these bottlenecks. Long Term Evolution Advanced (LTE-A), is a promising standard for 4G mobile networks, and it uses different technologies to enhance users’ performance regardless of their location in the coverage area. LTE-A employs Coordinated Multi-Point (CoMP) technique particularly to provide high data rate services for cell-edge users. In this context, we present Shared Segmented Upload (SSU), a novel method for uploading large files from User Equipment (UE) to multiple BSs in a CoMP communication scenario. We use Discrete EVent System Specification (DEVS) formalism to model an LTE-A mobile network using SSU. In addition, we employ DEVS to simulate a conventional non-cooperative algorithm to evaluate the effectiveness of SSU in two scenarios: rural and urban area settings. The simulation results show that, compared to the conventional method, SSU improves cell-edge users’ uplink performance and reduces the latency for a UE to upload its data to the network.

Collaborative Modeling Process for Development of Domain-Specific Discrete Event Simulation Systems

The discrete event systems specification (DEVS) formalism supports the object-oriented (OO) specification of discrete event models in a hierarchical, modular manner. If a system that is to be modeled is domain-specific, the development of models with the use of the DEVS formalism would require domain knowledge about the system as well as to understand DEVS semantics. This paper proposes a collaborative modeling process to compensate for the lack of professional engineers. To compensate, this modeling process utilizes three types of engineers: domain engineer, modeling and simulation (M&S) engineer, and platform engineer. The process consists of four steps: conceptual modeling, model partition, model implementation, and model integration/simulation. The system requirements are used to specify domain models in the conceptual modeling step, and the models are partitioned into two types: discrete event-level model (DEM) and behavioral-level model (BM). The DEM is specified as the DEVS formalism, and the BM is defined as algorithms and equations. Each model is implemented separately, and the implemented models are integrated and simulated flexibly by using a dynamic linking library. The modeling process is then applied to develop a war game simulator. The advantage of this modeling process is that the collaborative work is related to the whole series of steps. This collaboration maximally utilizes the capabilities of the professional engineers by seamlessly separating yet correlating their works.

A Qualitative Comparison of Two Hybrid DEVS Approaches

A hybrid system is defined as a system with mixed discrete event and continuous parts. Two ap- proaches for modeling and simulation of hybrid systems in the context of the Discrete EVent System Specification (DEVS) formalism are compared. Since the system theoret- ic DEVS approach has been introduced during the 1970ies, it has been completed by different extensions. The hybrid extensions checked against each other here, are the Quan- tized State Systems (QSS) method and a wrapper concept based on traditional ODE solvers. For a comparison from engineering practice point of view, these two hybrid DEVS approaches are analyzed within the scientific and technical computing environment MATLAB.

Discrete event modeling of swarm intelligence based routing in network systems

Simulation remains attractive for performance and scalability analysis and/or design of networks. This paper presents a biologically inspired discrete-event modeling approach for simulating alternative computer network protocols. This approach identifies and incorporates the key attributes of honeybees and their societal properties into simulation models that are formalized according to the Discrete Event System Specification (DEVS) formalism. We describe our approach with particular emphasis on how to model the individual honeybees and their cooperation. These models, collectively referred to as SwarmNet, support routing algorithms akin to honeybees searching for and foraging on food. Adaptation and probabilistic specifications are introduced into honeybee (BEE) and Routing Information Protocol (RIP) routing algorithms. A set of simulation experiments are developed to show the biologically inspired network modeling with the BEE routing algorithm, as compared with the RIP routing algorithm, offers favorable throughput and delay performance and also exhibit superior survivability against network load surges. The paper concludes with some observations on the SwarmNet modeling approach and outlines some future research directions.

Integrating Base Object Model Components into DEVS-based Simulation

The SISO standard Base Object Model (BOM) specification facilitates interoperability, re-usability, and composability of component models for simulation purposes. The common practice of constructing a BOM-based simulation system using the High-Level Architecture (HLA) does not, however, exploit the hierarchy of BOM components and hence limits re-usability. The Discrete EVent system Specification (DEVS) formalism has proven to be appropriate for hierarchical modeling and subsequent parallel and distributed simulation. In this paper we integrate the key part of the BOM, the component kernel, into a DEVS framework by mapping it onto atomic DEVS models. On the one hand, this precisely defines an automated mapping which fully conserves the wealth of information (such as hierarchy) present in BOMs. On the other hand, it allows for re-use of a plethora of theory, techniques and tools available for the DEVS formalism. If necessary, the DEVS models obtained through the integration can be optimized. A small case study of the take-off and landing of a plane demonstrates the increased re-usability compared to HLA-based approaches. This case study is also used to compare the performance of a BOM-based simulation system with the DEVS equivalent.

Research into simulation and modeling of material supply in emergent disaster based on DEVS/CD+

Dealing with emergent disaster is a typical discrete event system.Based on the analyses of Discrete Event System Specification(DEVS) formalism,the DEVS simulation model of material supply in the emergent disaster was made.The simulation entities were analyzed.The simulation flow was designed.The structures of coupled model and main atomic models were given.And the simulation test of this model was completed in CD++.The reasonable simulation results were obtained.It laid the foundation for the development of simulation training on the services of emergent disaster.

Socioeconomic modelling using the DEVS formalism

This paper deals with a new approach to the modelling of socioeconomic systems. In these models, there are many interacting entities (agents, players). The whole market comes up as a result of these interactions. In terms of the economy, this concept is based on the Subject-Need-Good triad. The subject in this model represents an economical subject with needs that can be satisfied by the consumption of a good. In terms of computational modelling, this concept is based on the Discrete Event System Specification (DEVS) formalism, where each subject is represented by one coupled DEVS. This coupled DEVS contains several atomic DEVS. There are only three types of atomic DEVS – generator/store, transformer and optimiser. The basic process of the concept is the transformation that changes one type of a good to another or uses a good to satisfy a need. This experimental frame will be used for the design and development of a new dynamic approach based on dynamic Petri nets.

Interactive evolutionary modelling and simulation of discrete-event systems using prototypical objects

In this paper, we describe an alternative approach to the traditional class-based approach of building simulation models using object-oriented languages. We use the Discrete EVent Systems specification (DEVS) formalism implemented by prototypical objects. The main reason why we use prototype-based object orientation for simulation modelling is the fact that it offers the level of flexibility that we need for interactive evolutionary modelling and simulation, which is used for simulation-based development of systems without exact specifications. We introduce a reflective framework model that constructs, inspects and edits the models specified using DEVS. The meta-object protocol of this framework allows the models to be constructed from scratch and inspected and edited during run-time. Interactive evolutionary modelling and simulation is supported by a visual tool set which has been highly influenced by the user interface of Self, an object-oriented language based on prototypical objects.

Security Simulation Modeling Using Contract Net Protocol

To solve the security problems which occur in the network such as Internet, we import software products of network security elements like an intrusion detection system (IDS) and a firewall. In this paper, we have designed and constructed the general simulation environment of network security model composed of multiple IDSs and a firewall, which coordinate by contract net protocol (CNP) for the effective detection of the intrusion. The CNP, the methodology for efficient integration of computer systems on heterogeneous environment such as distributed systems, is essentially a collection of agents which cooperate to resolve a problem. In the network security model, each model of simulation environment is hierarchically designed by discrete event system specification (DEVS) formalism. The purpose of this simulation is to evaluate the characteristics and performance of CNP architecture for the speeding up the inference cycle phases of the intrusion detection expert system.

Simulation Model Design of a Security System Based on a Policy-Based Framework

The management of network infrastructure is difficult and complex with the growth of the Internet. In an era of increasing technical complexity, it is becoming difficult to find trained personnel who can manage the new features introduced into the various servers, routers, and security systems. This article describes the modeling and simulation of a security system based on a policy-based framework that has some merits. Each component is implemented in a hybrid design using modeling concepts from discrete event system specification (DEVS) formalism and problem-solving concepts from the blackboard architecture of artificial intelligence. The authors propose that the intrusion detection system detects intrusions by using the blackboard and reports this information to the policy-based framework for automatic management. The policy server informs the firewall about this situation to prevent damage to the network.

DEVS-DOC: a modeling and simulation environment enabling distributed codesign

An approach to modeling and simulating distributed object computing systems as a set of software components mapped onto a set of networked processing nodes is presented. The modeling approach has clearly separated hardware and software components enabling systems level, distributed codesign engineering. The distributed codesign engineering refers to a system-theoretic approach to concurrent hardware and software systems engineering that provides a tractable method for analyzing the inherent complexities that arise in distributed computing systems. A software abstraction forms a distributed cooperative object (DCO) model to represent interacting software objects. A hardware abstraction forms a loosely coupled network (LCN) model of processing nodes, network gates and interconnecting communication links. The distribution of DCO software across LCN processors forms an object system mapping (OSM). This OSM provides a sufficient specification to allow simulation investigations. In simulation, the behavioral dynamics of the interacting DCO software components load and compete for LCN processing and networking resources. The LCN resource constraints thus impose performance constraints on the interactions of the DCO software objects. Class models of the DCO, LCN, and OSM component structures and behavior dynamics were formally characterized using the discrete event system specification (DEVs) formalism. These class model specifications were implemented in DEVSJAVA, a Java implementation of DEVS. Class models of experimental frame components were developed and implemented to facilitate analysis of the interdependent distributed system behaviors during simulations. Our DEVS-DOC M&S environment enables distributed systems architects, integration engineers and system designers to analyze performance and examine engineering trades of system structures, topologies and technologies. A case study demonstrates the ability to model and simulate a real world system and the complex interactions that arise in distributed computing systems.

Experiences with Devs Modelling and Simulation

This paper presents the results obtained with a tool used to model and simulate discrete event systems, based on Discrete Event systems Specification (DEVS) formalism. Its main features are presented and its use shown through application examples. The use of this formal approach allowed development of safe and cost-effective simulations. A simulated processor was built to study the different levels of a computer system. The goal was to help the full comprehension of the computer behaviour used in computer organization courses. The environment helped the students understand these complex systems and also allowed them to make empirical comparisons and performance studies for educational purposes.