24,320 research outputs found

    Consistency Algorithms and Protocols for Distributed Interactive Applications

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    The Internet has a major impact not only on how people retrieve information but also on how they communicate. Distributed interactive applications support the communication and collaboration of people through the sharing and manipulation of rich multimedia content via the Internet. Aside from shared text editors, meeting support systems, and distributed virtual environments, shared whiteboards are a prominent example of distributed interactive applications. They allow the presentation and joint editing of documents in video conferencing scenarios. The design of such a shared whiteboard application, the multimedia lecture board (mlb), is a main contribution of this thesis. Like many other distributed interactive applications, the mlb has a replicated architecture where each user runs an instance of the application. This has the distinct advantage that the application can be deployed in a lightweight fashion, without relying on a supporting server infrastructure. But at the same time, this peer-to-peer architecture raises a number of challenging problems: First, application data needs to be distributed among all instances. For this purpose, we present the network protocol RTP/I for the standardized communication of distributed interactive applications, and a novel application-level multicast protocol that realizes efficient group communication while taking application-level knowledge into account. Second, consistency control mechanisms are required to keep the replicated application data synchronized. We present the consistency control algorithms “local lag”, “Timewarp”, and “state request”, show how they can be combined, and discuss how to provide visual feedback so that the session members are able to handle conflicting actions. Finally, late-joining participants need to be initialized with the current application state before they are able to participate in a collaborative session. We propose a novel late-join algorithm, which is both flexible and scalable. All algorithms and protocols presented in this dissertation solve the aforementioned problems in a generic way. We demonstrate how they can be employed for the mlb as well as for other distributed interactive applications

    PERTS: A Prototyping Environment for Real-Time Systems

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    PERTS is a prototyping environment for real-time systems. It is being built incrementally and will contain basic building blocks of operating systems for time-critical applications, tools, and performance models for the analysis, evaluation and measurement of real-time systems and a simulation/emulation environment. It is designed to support the use and evaluation of new design approaches, experimentations with alternative system building blocks, and the analysis and performance profiling of prototype real-time systems

    A General Framework and Communication Protocol for the Real-Time Transmission of Interactive Media

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    In this paper we present a general framework for the real-time transmission ofinteractive media, i.e. media involving user interaction. Examples of interactive media are shared whiteboards, Java animations and VRML worlds. By identifying and supporting the common aspects of this media class the framework allows the development of generic services for network sessions involving the transmission of interactive media. Examples are mechanisms for late join and session recording. The proposed framework is based on the Real-Time Transport Protocol (RTP) which is widely used in the Internet for the real-time transmission of audio and video. Using the experience gained through the framework for audio and video, our work consists of three important parts: the definition of a protocol profile, the instantiation of this profile for specific media, and the development of generic services. The profile captures those aspects that are common to the class of interactive media. A single medium must instantiate this profile by providing media-specific information in the form of a payload type definition. Based on the profile, generic services can be developed for all interactive media. In this paper we focus on the description of the profile for the real-time transmission of interactive media. We then present the main ideas behind a generic recording service. Finally we show how multi-user VRML and distributed interactive Java animations can instantiate the profile

    Integration of decision support systems to improve decision support performance

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    Decision support system (DSS) is a well-established research and development area. Traditional isolated, stand-alone DSS has been recently facing new challenges. In order to improve the performance of DSS to meet the challenges, research has been actively carried out to develop integrated decision support systems (IDSS). This paper reviews the current research efforts with regard to the development of IDSS. The focus of the paper is on the integration aspect for IDSS through multiple perspectives, and the technologies that support this integration. More than 100 papers and software systems are discussed. Current research efforts and the development status of IDSS are explained, compared and classified. In addition, future trends and challenges in integration are outlined. The paper concludes that by addressing integration, better support will be provided to decision makers, with the expectation of both better decisions and improved decision making processes
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