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This paper describes the issues that are involved in designing and implementing a large‐scale cooperative object database server for a collaborative virtual environment. The focus of the paper is about the way to handle the distributing factors and the communication model among nodes within a collaborative virtual environment. Within the system, all objects are decentralized and scattered among three tiers of object databases. By limiting the knowledge and refining the tasks for each server, the network and processor workload can be reduced. The objective of the system is to provide a virtual environment for distributed computing that is k‐fault tolerant and subject to expansion without the interruption of services. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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The increasing popularity of multi‐player online games is leading to the widespread use of large‐scale Distributed Virtual Environments (DVEs) nowadays. In these systems, peer‐to‐peer (P2P) architectures have been proposed as an efficient and scalable solution for supporting massively multi‐player applications. However, the main challenge for P2P architectures consists of providing each avatar with updated information about which other avatars are its neighbors. This problem is known as the awareness problem. In this paper, we propose a comparative study of the performance provided by those awareness methods that are supposed to fully solve the awareness problem. This study is performed using well‐known performance metrics in distributed systems. Moreover, while the evaluations shown in the literature are performed by executing P2P simulations on a single (sequential) computer, this paper evaluates the performance of the considered methods on actually distributed systems. The evaluation results show that only a single method actually provides full awareness to avatars. This method also provides the best performance results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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As peer‐to‐peer (P2P) file‐sharing systems revolve around cooperation, the design of upload incentives has been one of the most important topics in P2P research for more than a decade. Several deployed systems, such as private BitTorrent communities, successfully manage to foster cooperation by banning peers when their sharing ratio becomes too low. Interestingly, recent measurements have shown that such systems tend to have an oversupply instead of an undersupply of bandwidth designers that have been obsessed with since the dawn of P2P. In such systems, the ‘selfish peer’ problem is finally solved, but a new problem has arisen: because peers have to keep up their sharing ratios, they now have to compete to upload. In this paper, we explore this new problem and show how even highly cooperative peers might in the end not survive the upload competition. On the basis of recent measurements of over half a million peers in private P2P communities, we propose and analyze several algorithms for uploader selection under oversupply. Our algorithms enable sustained sharing ratio enforcement and are easy to implement in both existing and new systems. Overall, we offer an important design consideration for the new generation of P2P systems in which selfishness is no longer an issue. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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随着网络时代的来临,网络教育迅猛发展.将虚拟现实技术（Virtual Reality）应用于网络教育中,结合网络教育的特点,可以仿真学校的校园环境.虚拟现实是计算机与用户之间的一种更为理想化的人-机界面形式,能够为学生提供生动、逼真的学习环境,学生能够成为虚拟环境的一名参与者,在虚拟环境中扮演一个角色.真实、互动、情节化的特点是虚拟现实技术独特的魅力所在. 相似文献
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虚拟教室系统共享白板工具设计及实现 总被引：1，自引：0，他引：1
该文主要根据基于CORBA和QoS使能的虚拟教室系统原型,讨论了系统共享白板工具的设计与实现方法。首先介绍了虚拟教室系统的系统结构,然后注重讲述了白板的图形文字编辑功能、白板数据的传输、白板通信机制的设计及实现。 相似文献
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This paper presents a technique to improve the performance of a walkthrough in remote virtual environments, where a scene is rendered jointly by the server and the client, in order to reduce the network requirements as much as possible. The client generates novel views by extrapolating a reference view based on the locally available geometric model, while the server transmits data necessary to prevent an accumulation of errors. Within this concept, we show that by transmitting only a selected subset of pixels, the quality of the extrapolated views can be improved while requiring less bandwidth. We focus on the selection process in which the visibility gaps between the reference view and novel view are detected, packed and transmitted compressed to the client. 相似文献
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虚拟现实技术在工程设计与分析上有很大的应用潜力。可是 ,虚拟环境的创建时间长、成本高,极大地限制了虚拟现实技术在工程上的应用。为此 ,提出了虚拟现实脚本生成器的概念,将虚拟现实技术与过程的设计、分析集成化,创造性地提出了一种自上而下的设计方法———VR-IEDA,以便高效、快速地创建虚拟原型,提高计算机虚拟复杂系统工程的性价比。在 VR-IEDA中复杂系统的结构和行为被计算机捕捉并自动生成可执行的 VR仿真代码 ,从而减少了创建虚拟环境的时间,便利了基于仿真的过程分析和设计。最后 ,以武器系统的维修过程为 相似文献
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Wen-Yan Wu School of Computing Engineering & Technology Sta?ordshire University Sta?ord ST AD UK Zheng-Xu Zhao Virtual Reality Research Technology Center Southeast University Nanjing PRC 《国际自动化与计算杂志》2005,2(1):25-36
1 Introduction The scalability of virtual environments (VEs) that allow users to change and modify their contents and context depending on application requirements has been a de facto feature of virtual reality technology. Engineering uses such as virtual testing and exper- imenting applications demand VEs to be highly or fully reconfigurable. In reality, however, satisfactory reconfiguration of a virtual environment is yet to be achieved, due to the high accuracy of spatial data in- put and… 相似文献
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Marinho Pilla Barcellos Luciano Paschoal Gaspary Weverton Luis da Costa Cordeiro Rodolfo Stoffel Antunes 《Concurrency and Computation》2011,23(1):117-141
Despite being currently one of the main Internet applications, P2P file sharing has been hampered by content pollution attacks. To tackle this problem, we introduce a novel pollution control strategy that consists in adjusting the rate in which content is disseminated, according to content version reputation. The proposed strategy is modeled and evaluated using simplifying assumptions. Then, inspired by classic distributed designs, we propose a pollution control mechanism that implements such a strategy. The mechanism is evaluated in terms of the delays imposed on non‐polluted version dissemination, the effectiveness of reducing dissemination when the version is polluted, and the negative impact that collusion attacks can impose on the reputation system upon which our mechanism is built. Simulation results looking at scenarios with several hundred peers indicate that the pollution control mechanism can effectively reduce pollution without substantially affecting the dissemination of non‐polluted content. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Niels Drost Rob V. van Nieuwpoort Jason Maassen Frank J. Seinstra Henri E. Bal 《Concurrency and Computation》2011,23(13):1506-1521
The inherent complex nature of current distributed computing architectures hinders the widespread adoption of these systems for mainstream use. In general, users have access to a highly heterogeneous set of compute resources, which may include clusters, grids, desktop grids, clouds, and other compute platforms. This heterogeneity is especially problematic when running parallel and distributed applications. Software is needed which easily combines as many resources as possible into one coherent computing platform. In this paper, we introduce Zorilla: peer‐to‐peer (P2P) middleware that creates a single distributed environment from any available set of compute resources. Zorilla imposes minimal requirements on the resource used, is platform independent, and does not rely on central components. In addition to providing functionality on bare resources, Zorilla can exploit locally available middleware. Zorilla explicitly supports distributed and parallel applications, and allows resources from multiple sites to cooperate in a single computation. Zorilla makes extensive use of both virtualization and P2P techniques. We will demonstrate how virtualization and P2P combine into a simple design, while enhancing functionality and ease of use. Together, these techniques bring our goal a step closer: transparent, easy use of resources, even on very heterogeneous distributed systems. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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A peer‐to‐peer (P2P) characterization model is proposed in this paper. The purposes of this model are (a) to describe through abstraction the behavior and capability of P2P computing independent of any specific application, and (b) to lead to a cost model of P2P computing. Our approach is based on abstracting the service driven nature of P2P computing separate and distinct from its implementation. This supports the first purpose. Next, we consider the integration of the two aspects. This supports the second purpose. A secondary contribution of our work is a cost model. The cost model is applied to indexing, discovery and resource utilization services. In addition, the characterization model and cost model are applied to a JXTA‐based P2P application. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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面向分布式虚拟设计的协同工作环境研究 总被引：10，自引：0，他引：10
为了实现分布式虚拟设计过程中的信息共享、协作以及冲突消解,建立了一个面向分布式虚拟设计的协同工作环境．描述了系统体系模型的研究方法和基于CORBA的多层分布式结构,详细介绍了基于TCP／IP协议和基于面向对象的运行时期类型信息(Run Time Type Information,RTTI)技术的实体实时通信协议的技术内涵、执行流程和设计实现,该协议用于保持网络中不同结点的几何模型在实体级别上的一致性．对分布式虚拟设计中的并发性问题进行了探讨,采用实体锁定机制实现了某些环节的冲突消解,并对几种实体锁定的仲裁方法进行了比较． 相似文献