Distributed Web-Based Simulation
Yuh-Chyun Luo (Chung-Cheng Institute of Technology), Chun-Hung Chen (George Mason University), Enver Yücesan (INSEAD) and Insup Lee (University of Pennsylvania)
Web technology is having a significant impact on computer simulation. Most of the effort in web-based simulation is aimed at modeling, particularly at building simulation languages and at creating model libraries that can be assembled and executed over the web. We focus on the efficiency of simulation experimentation for optimization. We introduce a framework for combining the statistical efficiency of simulation optimization techniques with the effectiveness of parallel execution algorithms. In particular, the Optimal Computing Budget Allocation (OCBA) algorithm is implemented in a web-based environment for low-cost parallel and distributed simulation experimentation. A prototype implementation with some experimental results is presented.
The Monarc Toolset for Simulating Large
Network-Distributed Processing Systems
Iosif C. Legrand and Harvey B. Newman (California Institute of Technology)
The next generation of High Energy Physics experiments have envisaged the use of network-distributed Petabyte-scale data handling and computing systems of unprecedented complexity. The general concept is that of a "Data Grid Hierarchy" in which the central facility at the European Laboratory for Particle Physics (CERN) in Geneva will interact and coherently manage tasks shared by and distributed amongst national "Tier1 (National) Regional Centres" situated in the US, Europe, and Asia. CERN and the Tier1 Centers will further communicate and task-share with the Tier2 Regional Centers, Tier3 centers serving individual universities or research groups, and thousands of "Tier4" desktops and small servers. The design and optimization of systems with this level of complexity requires a realistic description and modeling of the data access patterns, the data flow across the local and wide area networks, and the scheduling and workload presented by hundreds of jobs running concurrently on large scale distributed systems exchanging very large amounts of data. The simulation toolset developed within the "Models Of Networked Analysis at Regional Centers" - MONARC project provides a code and execution time-efficient design and optimisation framework for large scale distributed systems. A process-oriented approach for discrete event simulation has been adopted because it is well suited to describe various activities running concurrently, as well the stochastic arrival patterns typical of this class of simulations. Threaded objects or "Active Objects" provide a natural way to map the specific behaviour of distributed data processing (and the required flows of data across the networks) into the simulation program.
Object-Oriented Simulation of Distributed Systems
Using Java® and Silk®
Richard A. Kilgore (ThreadTec, Inc.) and Emmett Burke (Symbi Systems, Inc.)
An object-oriented modeling infrastructure using the Java-based, Silk simulation classes is defined that enables the simulation of multitasking, distributed systems using symmetric multiprocessors. The simulation infrastructure is being used to evaluate alternative architectures for embedded, distributed systems. We show how the underlying structure is adapted to several different applications, including various Internet applications. The paper describes the infrastructure, its robustness, and the application of the model to produce insights for a system under design. The simulation infrastructure enables a high fidelity representation of the internal complexity of the application on each processing node, the operating system behavior, and the disks and network. The simple yet powerful representation leverages the use of the Silk entity-thread architecture to achieve a simulation architecture that maps to the actual system architecture in both conceptual design and processing sequence. The model has been validated through instrumentation of the evolving target system.
A Web-Based Interface for Storing and Executing
Ashu Guru, Paul Savory, and Robert Williams (University of Nebraska)
The dominance of the Internet in the development of information and communication technology has made Web-based distributed solutions increasingly attractive. Apart from providing other services, the World Wide Web is being looked upon as an environment for hosting modeling and simulation applications. SIMAN is a simulation language that allows users to simulate discrete and continuous systems. In this research, a web-based interface or toolkit has been developed for storing and executing SIMAN simulation models over the Internet. This toolkit consists of a World Wide Web interface to SIMAN and a web-accessible database for storing user models. It provides users an easy-to-use environment for developing text-based simulation models using the SIMAN simulation language. It also allows users to test the functionality of a SIMAN model using the SIMAN debugger/run controller.
A Java-Based Simulation Manager for Web-Based
Charles Marr and Christopher Storey (US Army), William E. Biles (University of Louisville) and Jack P.C. Kleijnen (Tilburg University)
This paper discusses a Web-based simulation manager program that executes an Application Service Provider (ASP) event for a customer who does not possess the in-house capability to program complex simulations. The utility in using this simulation manager is that the customer needs results in near real-time; that is, approximately the time to run one complete replication of the simulation model plus some overhead time to send the commands necessary to execute the simulation and to process the results. The simulation manager executes simulation studies in a parallel replications format, using either designed experiments or optimization methodologies, by sending the appropriate messages to a set of engine processors to cause the execution of the prescribed simulation trials. It then receives and analyzes the simulation results produced by the simulation engines, and sends a project report to the human customer.
An Interactive Land Use VRML Application (ILUVA) with
Lee A. Belfore, II and Suresh Chitithoti (Old Dominion University)
We summarize progress achieved on an interactive land use VRML application (ILUVA) with servlet assist. The purpose of this application is to enable one to take a virtual land area and add buildings, roadways, landscaping and other features. The application is implemented entirely using standard web based technologies to allow fairly universal accessibility. The Virtual Reality Modeling Language (VRML) is a programming language that describes three dimensional objects and defines interactions associated with these objects. In this work, we show how the interactive capabilities can be expanded by employing Java servlets for recording user actions and for restoring prior sessions. The Java servlets offer several powerful capabilities including enabling logging permanent records of user sessions, retrieval of prior sessions, and dynamically generated VRML.
A Model-Based Approach for Component Simulation
Perakath Benjamin, Dursun Delen, and Richard Mayer (Knowledge Based Systems, Inc.) and Timothy O’Brien (John F. Kennedy Space Center, NASA)
The increasing complexity of systems has enhanced the use of simulation as a decision-support tool. Often, simulation is the only scientific methodology available to practitioners for the analysis of complex systems. However, only a small fraction of the practical benefits of simulation modeling and analysis have reached the potentially large user community because of the relatively high requirement of time, effort, and cost needed to build and successfully use simulation models. In this paper we describe a model-based approach that seeks to address these problems via the implementation of MODELSIM––a comprehensive modeling and analysis architecture that includes (i) application of the IDEF3 and IDEF5 methods for simulation modeling and analysis specification, (ii) automatic generation of executable component-based simulations from IDEF-based descriptive models, and (iii) reusable libraries of modeling components to facilitate rapid configuration of models as needed over extended periods of time.
Dynamic Component Substitution in Web-Based
Dhananjai Madhava Rao and Philip A. Wilsey (University of Cincinnati)
Recent breakthroughs in communication and software engineering has resulted in significant growth of web-based computing. Web-based techniques have been employed for modeling, simulation, and analysis of systems. The models are commonly developed using component based techniques where a system is represented as a set of interconnected components. A component is a well-defined software module that is viewed as a ``black box'' element. However, the behavior of a component, which is necessary for simulation, can be implemented by different modelers including third party manufacturers. Web-based simulation environments enable effective sharing and reuse of components thereby minimizing model development overheads. In component based simulations, one or more components can be substituted during simulation with a functionally equivalent set of components. Such Dynamic Component Substitutions(DCS) provide an effective technique for selectively changing the level of abstraction of a model during simulation. It provides a tradeoff between simulation overheads and model details. It can be used to effectively study large systems and accelerate rare event simulations to desired scenarios of interest. DCS may also be used to achieve fault-tolerance in Web-based simulations. This paper presents the ongoing research to design and implement support for DCS in A Web-based Environment for Systems Engineering (\wese).
Finding a Substrate for Federated Components on the
John A. Miller, Andrew F. Seila, and Junxiu Tao (University of Georgia)
Recent developments in software component technology have renewed the promise of reusable software. Combining this with the possibilities of sharing simulation results and models using the Internet makes these new developments all the more important, particularly for Web-Based Simulation. Interoperability standards and data interchanges standards (e.g., XML) help facilitate having simulation models interact with other simulation models as well as other information technology components. This paper examines newer component technologies such as Enterprise Java Beans (EJB) and Jini in a search for an ideal substrate for Web-Based Simulation. Components will need distributed capabilities as well as the ability to flexibly and dynamically join an existing group of interacting components (referred to as a federation).
SIMFONE´: An Object-Oriented Simulation
Manuel D. Rossetti (University of Arkansas) and Ben Aylor, Ryan Jacoby, Alyson Prorock, and Antoine White (University of Virginia)
This paper presents an overview of a software design framework for the development of object-oriented simula-tions. The framework is documented using the Unified Modeling Language (UML) and is divided into packages to organize the collection of classes into important functional areas. The purpose of the framework is two-fold. First, the framework is useful in understanding the concepts and abstractions within simulation modeling and languages. Secondly, the framework can serve as the basis for the de-velopment of object-oriented simulation libraries. We illustrate the latter through a Java implementation.
VisualSLX - An Open User Shell for High-Performance
Modeling and Simulation
Thomas Wiedemann (Technical University of Berlin)
SLX by Wolverine software is actually one of the fastest simulation languages. Besides the high performance the SLX-compiler can be extended very easily by user specific syntax rules and new basic functions. This "pyramid power" of SLX is used to build a new system for modeling and simulation - VisualSLX. This system is a shell atop the standard SLX-compiler and the runtime system. All model and simulation data are stored in a universal data-base. VisualSLX could be used for a comfortable, rapid visual modeling and for remote modeling and simulation through the internet without any knowledge of the SLX-syntax and modeling paradigms. This paper reveals the architecture and the underlying data structures of the system. Additional requirements and interfaces are caused by the application of VisalSLX as a web-based modeling and simulation system.
A Review of Web Based Simulation: Whither We
Jasna Kuljis and Ray J. Paul (Brunel University)
This paper considers a variety of new technologies for discrete-event simulation software development. Environments and languages for web based simulation are reviewed. Web based applications are discussed. After proposing a summary of the review, ways of working that will have an unpredictable effect on the future of simulation modeling are proposed.
Issues in Java-Based Continuous Time Step Physical
Lisa A. Schaefer (The MITRE Corporation) and Philip M. Wolfe (Arizona State University)
This paper discusses the problems involved in developing a Java based simulation model of autonomous entities that can navigate themselves in 2-dimensional space. We develop some ideas for solving those problems. The ideas mentioned in this paper can be applied to simulations that have fuzzy logic for navigation, encapsulation for object-oriented simulation, many instances of objects, or statistically complex results. We cite reasons for distributing a simulation among several computers and propose several topics for future research.
Java Engine for UML Based Hybrid State
Andrei V. Borshchev, Yuri B. Kolesov, and Yuri B. Senichenkov (St. Petersburg Technical University)
One of the approaches to modeling hybrid systems is to assign algebraic-differential equations describing the continuous behavior to states of state machines that represent discrete logic. The resulting hybrid state machine is a powerful concept to specify complex interdependencies between discrete and continuous time behaviors. It, however, exposes the simulation engine to a number of problems, which we discuss. The hybrid state machine based approach presented in this paper is fully supported by UML-RT/Java tool developed at Experimental Object Technologies.