Log-based Middleware for Pervasive Application Sharing

无处不在的应用程序共享使用户能够进行协作，而无需考虑其计算设备、网络、应用程序和位置。更具体地说，它允许分布式用户共享应用程序以(I)使用具有不同功能的固定和移动计算机，例如服务器、PC、手持设备、掌上电脑和手机；(Ii)根据计算机的位置动态地切换计算机，将会话状态从一台计算机迁移到另一台计算机；(Iii)高效地在离线和在线模式之间切换；(Iv)使用仅连接当前活动合作者的计算机的最小网络；以及(V)改变共享体系结构以适应网络连接的变化。现有的应用程序共享基础设施并没有被设计成支持所有这些属性。假设是“通过开发一种新的基于日志的机制来跨网络分发I/O事件来支持所有这些需求是可能的”。更具体地说，可以通过以下方式来支持这些需求：(I)设计一种新形式的日志记录，称为基于对象的日志记录，它结合了传统日志记录和状态转移的优点，从而改善了传统日志记录的空间和时间开销；(2)基于基于对象的日志记录开发了一种共享机制，该机制可以支持(A)到目前为止已经提出或开发的所有应用程序共享体系结构，以及(B)这些体系结构之间的任意动态转换；(3)提供该机制作为中间件(即，应用程序和系统组件之间的层)；在这个项目中，试图通过开发这四个想法来验证这一假设，并在基于Java的机制中实现它们，并对该机制进行评估，以确定它的空间和时间效率，它为应用程序开发人员提供了多大程度的自动化，以及它可以支持多少不同类型的新的和现有的应用程序、系统层和网络配置。为了执行这些评估，这项工作将使用该机制来支持由几个有影响力的用户界面工具/框架定义的I/O事件共享，这些工具/框架包括VNC网络帧缓冲区、X网络窗口系统、Java Swing工具包以及模型视图控制器和Java Beans框架。如果成功，这项工作将导致协作支持，这些支持可以部署在更广泛的(设备、网络、系统层和应用程序)配置中，并已通过实际用户协作研究和信息的可用性测试。

Pervasive application-sharing allows users to collaborate regardless of their computing device, network, application, and location. More specifically, it allows distributed users sharing an application to (i) use stationary and mobile computers with varying capabilities such as servers, PCs, hand-helds, palmtops, and cell phones; (ii) dynamically switch computers based on their location, migrating session state from one computer to another; (iii) efficiently switch between offline and online modes; (iv) use a minimal network connecting only the computers of the currently active collaborators, and (v) change the sharing architecture to adapt to changes in network connectivity. Existing application-sharing infrastructures have not been designed to support all of these properties.The hypothesis is "it is possible to support all of these requirements by developing a novel log-based mechanism for distributing I/O events across the network". More specifically, one can support these requirements by (I) designing a new form of logging, called object-based logging, that combines benefits of traditional logging and state transfer, thereby improving the space and time overheads of traditional logging; (2) developing a sharing mechanism based on object-based logging that can support (a) all application-sharing architectures that have been proposed or developed so far, and (b) arbitrary dynamic transitions among these architectures; (3) providing this mechanism as middleware (that is, a layer between application and system components); and (4) tying the mechanism, not to a particular system component such as a network windowing system, but instead a general design pattern for creating applications.In this project, an attempt to verify this hypothesis by developing these four ideas, implementing them in a Java-based mechanism, and evaluating the mechanism to determine how space and time efficient it is, how much automation it provides to application developers, and how many different kinds of new and existing applications, system layers, and network configurations it can support. To perform these evaluations, the work will use this mechanism to support sharing of I/O events defined by several influential user-interface tools/frameworks including the VNC network frame buffer, the X network window system, the Java Swing toolkit, and the Model View Controller and Java Beans frameworks.If successful, the work will lead to collaborative support that can be deployed in a much wider range of (device, network, system layer, and application) configurations and has been tested for usability by real users collaborative research and information.