Don McGregor

NPSNET-V. A new beginning for dynamically extensible virtual environments

At the Naval Postgraduate School (NPS) we, like others in the collaborative VE community, have extolled the virtues of persistent online virtual worlds for years. We previously addressed the infrastructure requirements of a large-scale, persistent online virtual world: runtime extensibility of both content and applications; scalability in world complexity and number of participants; and composability of heterogeneous content and applications. We follow those arguments with the first publication describing NPSNET-V.

A unified component framework for dynamically extensible virtual environments

If large-scale shared virtual worlds are to be established on the Internet, they must be based on technologies that allow them to adapt, scale, and evolve continuously-that is, without their being taken offline. In the course of designing NPSNET-V, an architecture intended to satisfy these criteria through component-based dynamic extensibility, the authors recognized the need for a consistent, unified component framework. This framework, which they implemented in Java™, allows one to construct applications as component hierarchies rooted at an invariant microkernel. A simple extensible interface layer and event model allow components to communicate with one another, and an XML configuration and serialization mechanism permits applications to store and transmit component and application state in a versatile standardized format. After an initial bootstrapping process, one may add, remove, and upgrade components at run time, and one may introduce newly loaded Java™ code anywhere in the application hierarchy at any time. The complications posed by this reconfigurability and the hierarchical nature of NPSNET-V applications led the authors to develop a consistent design strategy, which they based largely on several common design patterns. The most critical design pattern that they used was the Model-View-Controller pattern, which forms the basis of the NPSNET-V entity model.

Requirements for large-scale networked virtual environments

Proceedings of the 7th International Conference on Telecommunications ConTel 2003, Zagreb, Croatia, 11-13 June 2003, pp. 353-358.

Security of runtime extensible virtual environments

Distributed, real-time virtual environment (VE) architectures have traditionally been driven by quality of service (QOS) considerations, with little or no concern paid to security issues. With recent advancements in functionality, computing power and network bandwidth it has become practical to use VEs in sensitive areas such as product development with proprietary information and visualization of classified information. Consequently, previously ignored aspects of security need to be made a primary concern at the outset of designing a VE. In this paper we explore security concerns associated with a subtype of VEs: Runtime Extensible VEs (RTEVEs). We introduce a taxonomy of security issues, derived from a case study of NPSNET-V, with the goal of using this taxonomy to guide the formulation of security policy, requirements, and architectures for RTEVEs.

X3D distributed interactive simulation (DIS) implementation and run-time discovery of new entities using X3DOM

New capabilities in web browser JavaScript implementations including networking, improved graphics performance, and improved speed allow the implementation of Networked Virtual Environments (NVEs) inside the web browser. An NVE can be written in JavaScript, which enables deployment in the enterprise entirely from a web server without the use of browser plugins. We discuss one implementation of this idea using X3DOM, an open-source implementation of the X3D standard written in JavaScript. The Open-DIS library for the IEEE Distributed Interactive Simulation (DIS) network protocol is used to create a partial implementation of the X3D standards DIS profile. Mechanisms for using the X3D DIS Profile DISEntityTypeMapping and DISEntityManager to enable run-time discovery and launching of new entities are discussed. Measurements of the capabilities and performance aspects of Websockets for network transport demonstrate excellent results.

A hands-on introduction to networked virtual environments

Networked virtual environments enable us to grow from using single-player machines to interacting across distances with players on other machines. Building a networked virtual environment is a significant software development effort, but we are getting to the point where we can build some systems routinely. This course provides an overview of the current state-ofthe-art with respect to networked virtual environments, where the hard research work is yet to be done and a hands-on introduction to the NPSNET-V. NPSNET-V is a research effort intended to investigate dynamically extensible, large-scale virtual environments. It is a follow-up to the successful NPSNET-IV project and builds on the lessons learned in that effort. The NPSNET-V effort includes research in support for the dynamic loading of simulation components across the network, the dynamic modification of object behaviors and protocols, scalability in numbers of world clients and overall world size, persistence, and graphics standard agnosticism.