J. Mark Pullen

Using Web services to integrate heterogeneous simulations in a grid environment

The distributed information technologies collectively known as Web services recently have demonstrated powerful capabilities for scalable interoperation of heterogeneous software across a wide variety of networked platforms. This approach supports a rapid integration cycle and shows promise for ultimately supporting automatic composability of services using discovery via registries. This paper presents a rationale for extending Web services to distributed simulation environments, together with a description and examples of the integration methodology used to develop significant prototype implementations, and argues for combining the power of Grid computing with Web services to further expand this demanding computation and database access environment.

Accurate Depth of Field Simulation in Real Time

We present a new post processing method of simulating depth of field based on accurate calculations of circles of confusion. Compared to previous work, our method derives actual scene depth information directly from the existing depth buffer, requires no specialized rendering passes, and allows easy integration into existing rendering applications. Our implementation uses an adaptive, two‐pass filter, producing a high quality depth of field effect that can be executed entirely on the GPU, taking advantage of the parallelism of modern graphics cards and permitting real time performance when applied to large numbers of pixels.

Extensible Battle Management Language as a Transformation Enabler

This article addresses a new approach to the longstanding problem of interoperating military command and control with combat simulations. There is great potential benefit in such a capability, both for more effective training and as a “what if” capability during military operations. The authors describe the Battle Management Language (BML), an unambiguous means of describing military operations to people, simulations, and robotic forces. The process that developed the BML and its extension into the realm of Web services are described. The new capability is projected to be an enabler for the ongoing transformation activities in the U.S. Department of Defense. Integrated with the Command and Control Information Exchange Data Model (C2IEDM), BML, as extended through Web services, provides a path to improved interoperability within and among U.S. military services and their allied/coalition partners.

Integrating synchronous and asynchronous internet distributed education for maximum effectiveness

Distributed education delivered via the Internet is a growing practice, with most institutions offering at least course websites and many expanding to full course offerings and even online degree progams. There are two schools of thought with regard to delivery mode: the larger group has focused on asynchronous delivery, accessible at any time via webpages and interactive tutorials and quizzes, while a smaller group advocates synchronous delivery where students are online and interact during class time. This paper summarizes the advantages and disadvantages of the two delivery modes and describes our successful and growing experience of more than a decade using an open source synchronous delivery tool blended with a variety of asynchronous capabilities and classroom instruction. We conclude that a synergistic combination of the two modes with in-person instruction, designed to provide maximum flexibility to the student within the constraints of the subject, offers the best support for student learning.

Using Web Services to Integrate Heterogeneous Simulations in a Grid Environment

The distributed information technologies collectively known as Web services recently have demonstrated powerful capabilities for scalable interoperation of heterogeneous software across a wide variety of networked platforms. This approach supports a rapid integration cycle and shows promise for ultimately supporting automatic composability of services using discovery via registries. This paper presents a rationale for extending Web services to distributed simulation environments, including the High Level Architecture (HLA), together with a description and examples of the integration methodology used to develop significant prototype implementations. A logical next step is combining the power of Grid computing with Web services to facilitate rapid integration in a demanding computation and database access environment. This combination, which has been called Grid services, is an emerging research area with challenging problems to be faced in bringing Web services and Grid computing together effectively.

The network workbench: network simulation software for academic investigation of Internet concepts

Abstract Simulation offers significant advantages as a basis for academic projects in computer networking. Because many unimportant details can be abstracted away, and also because simulations can be completely repeatable, it is possible to address the same concepts more quickly than is possible with actual networks. At the same time, students who program a protocol for a network simulator come to understand the protocol much better than if they learn only from reading and lectures. This paper reports on a new network simulator, the Network Workbench, which is intended for use in the academic environment. It is based on discrete event simulation and structured around a five-layer stack abstracted from the Internet protocols (TCP/IP family). While the Workbench is less powerful than some tools used for investigation of larger networks or more complex protocols, it has compensating advantages. Its use can be learned quickly and it is sufficiently powerful, comprehensive, and extensible to allow investigation of a considerable range of problems. The Workbench, which is available to the academic community under no-cost license, includes a set of protocol programming exercises for introductory networking courses and it also has proved usable for more advanced student research projects. This paper describes the philosophy behind the Workbench, gives a brief outline of its history, explains its internal structure, and describes its use in computer network teaching and research.

The Internet-based lecture: converging teaching and technology

Network-based distributed education is a reality today. At George Mason University, we have been pursuing a capability beyond the widespread practice of supporting courses with webpages: delivering lectures and seminars in real time, over the Internet. This paper describes the range of distributed education technologies available today, focusing on issues of instructor presentation, student participation, and temporal qualities of response to student questions. The analysis supports our selection of desktop audiographics for synchronous Internet-based course delivery. Courses that have been presented in this mode are described, along with factors influencing their success and factors in student participation.

Networking for distributed virtual simulation

Abstract Distributed Virtual Simulation (DVS) is a new technology that extends Virtual Reality to the networked environment. It was developed for military training and is being used for civilian education and entertainment. Participants can interact over great distances in the virtual world if supported by a network that provides real-time, multicast packet communications with resource reservation for adequate performance, and satisfactory security. Requirements and techniques for real-time networking, internetted multicast, and resource reservations in support of DVS are described, and are used to define the set of missing Internet technologies that will be needed for DVS.

Scaling up a distance education program in computer science

This paper describes issues and their solutions in presenting a graduate program in distance education online. The author developed significant experience in synchronous Internet distributed education by experimental teaching online. This process has produced an open-source software system for synchronous online teaching and learning, Network EducationWare. That system is described, along with experience in expanding its use from one course to a graduate Computer Science degree program. Detailed discussions elaborate problems encountered and their solutions. Experience has shown that online teaching in this format is beneficial to students, supportable by faculty, and affordable by the educational institution, in part due to the effective implementation described.

The Network Workbench and Constructivism: Learning Protocols by Programming

The Network Workbench (NW) is a software environment for academic investigation of network protocol concepts. The structure and operation of NW has been described in detail elsewhere. This paper addresses the instructional design of NW with the intention of establishing that it represents ‘natural constructivism’ in that it is strongly aligned with the constructivist approach. We begin with a synopsis of constructivist educational philosophy. After this the architecture of NW and the facilities it provides are described, as are the 12 associated protocol programming projects. Based on these descriptions, the design of NW and its projects are evaluated in light of principles of the constructivist educational philosophy and shown to be in very strong alignment with them. We conclude that, although its development did not proceed from a formal grounding in constructivism, NW represents successful implementation of constructivist philosophy as a natural approach to teaching protocols for computer networking.