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Browsing by Author "Chiao, HT"

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    A component-based, reconfigurable mobile agent system for context-aware computing
    (2002)
    Chiao, HT
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    Cheng, MC
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    Chang, YS
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    Yuan, SM
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    資訊工程學系
    In the near future, people can use various kinds of portable terminal devices, such as PDAs or smart phones, to access,the information on Internet at any time, in any place, for supporting their daily life. Personal mobile agents can help those people to search, to filter, to analyze, or to translate the large amount of Internet information. Since the context of a user may vary frequently, the way a personal mobile agent process the Internet information must adapt to the context change. However, we think that the current mainstream mobile agent platforms, such as the IBM Aglet and the IKV++ Grasshopper, are not good enough for developing context-aware applications. Hence, we propose a Component-based, Reconfigurable Mobile Agent (CRMA) system, which is designed for context-aware computing. It offers downloadable user-interface modules on terminal devices for application to adapt the characteristics of various terminal devices. In addition, on agent side, CRMA provides a reconfigurable agent-programming framework, which uses component-based pipelines to perform context-aware data-processing operations. This not only simplifies the programming task for dynamically reconfiguring an agent's behavior to adapt the context change, but also improves the reusability of agent software. In the end of this paper, we will propose a context-aware meta-search service to demonstrate how to use CRMA to develop a context-aware application.
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    A more expressive monitor for concurrent Java programming
    (2000)
    Chiao, HT
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    Wu, CH
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    Yuan, SM
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    資訊工程學系
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    Department of Computer Science
    The thread synchronization mechanism employed by Java is derived from the Hoare's monitor concept. In order to minimize its implementation complexity, the monitor provided by Java is quite primitive. This design decision prefers simple concurrent objects and single-thread programs. However, we think the Java monitor is over simplified for developing more elaborated concurrent objects. Besides, several features of the Java monitor will bring extra overhead when thread contention gets higher. Currently, we have identified five drawbacks of the Java monitor. In this paper, we will first analyze these drawbacks in depth, and then propose a new monitor-based synchronization mechanism called EMonior. It has better expressive power, and introduces fewer overheads than the Java monitor when contention occurs. EMonior uses a preprocessor to translate the Java programs containing EMonitor syntax to regular Java programs that invoke EMonitor class libraries. It is very suitable to replace the Java monitor with the EMonitor when developing elaborate concurrent objects or high-contention concurrent systems.
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    A portable real-time extension set for Java
    (2001)
    Chiao, HT
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    Huang, ST
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    Kao, SHJ
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    Yuan, SM
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    資訊工程學系
    Since the fourth quarter of 1999, the authors engaged in a project where Java was employed to build the real-time control program inside a plastic-injection-molding machine. However, at that time, since the official real-time Java standard - the Real-Time Specification for Java (RTSJ) from the Sun Microsystems was still under development, no RTSJ-compliant Java virtual machine was available. To satisfy our requirement, we designed and implemented a real-time extension library for enhancing the Java virtual machine that was already available in the real-time operating system we used. Our extension library has the following advantages: First, the underlying Java virtual machine needs no modification to accommodate it. Second, this extension library is easy to be ported to any other priority-based real-time operating systems. Third, the core of this extension library is basically derived from the subset of the RTSJ public draft, and thus our real-time control program can be move to a forthcoming RTSJ-compliant Java virtual machine without much difficulty. In brief, our work may help suggest ways of implementing RTSJ, or the notion of (degrees of) "minimal" compliance/support of RTSJ based on non-RTSJ Java virtual machines. In this paper, we will show the requirement, application programming interface, and implementation of this extension library, and discuss its influence on timing.
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    An enhanced thread synchronization mechanism for Java
    (2001-06-01)
    Chiao, HT
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    Yuan, SM
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    資訊工程學系
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    Department of Computer Science
    The thread synchronization mechanism of Java is derived from Hoare's monitor concept. In the authors' view, however, it is over simplified and suffers the following four drawbacks. First, it belongs to a category of no-priority monitor, the design of which, as reported in the literature on concurrent programming, is not well rated. Second, it offers only one condition queue. Where more than one long-term synchronization event is required, this restriction both degrades performance and further complicates the ordering problems that a no-priority monitor presents. Third, it lacks the support for building more elaborate scheduling programs. Fourth, during nested monitor invocations, deadlock may occur In this paper we first analyze these drawbacks in depth before proceeding to present our own proposal, which is a new monitor-based thread synchronization mechanism that we term EMonitor This mechanism is implemented solely by Java, thus avoiding the need for any modification to the underlying Java Virtual Machine. A preprocessor is employed to translate the EMonitor syntax into the pure Java codes that invoke the EMonitor class libraries. We conclude with a comparison of the performance of the two monitors and allow the experimental results to demonstrate that, in most cases, replacing the Java version with the EMonitor version for developing concurrent Java objects is perfectly feasible. Copyright (C) 2001 John Wiley & Sons, Ltd.
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    Experience in building a real-time extension library for Java
    (2002-11-01)
    Chiao, HT
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    Kao, SHJ
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    Chang, YS
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    Huang, ST
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    Yuan, SM
    For building real-time control programs on PC controllers, we designed and implemented a real-time extension library to enhance the Java virtual machine that was already available in the real-time operating system we used. Our extension library has the following advantages: First, the underlying Java virtual machine needs no modification to accommodate it. Second, this extension library is easily ported to any other priority-based real-time operating system. Third, the core of this extension library is basically derived from a subset of the Real-Time Specification for Java (RTSJ) standard, and thus our real-time control program can be moved to a forthcoming RTSJ-compliant Java virtual machine without much difficulty. In brief, our work may help suggest ways of implementing RTSJ, or the notion of (degrees of) "minimal" compliance/support of RTSJ based on non-RTSJ Java virtual machines. In this paper, we will show the requirement, application programming interface, and implementation of this extension library, and discuss its influence on timing.
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    FJM: a high performance Java Message Library
    (2003)
    Hsiao, TY
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    Cheng, MC
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    Chiao, HT
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    Yuan, SM
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    資訊工程學系
    In this paper, we presented an IP-multicast-based Java Message Service implementation called FJM (Fast Java Messaging) Library. We discussed its architecture, protocols, and implementation issues. For achieving better performance, we revised the original design of the FJM. The details of the refinement were also described in this paper. Then, we compared the performance of the both versions of the FJM with the performance of other JMS implementations. After our carefully design and tuning, in most cases, the revised version of the FJM can offer the highest throughput among the well-known industrial or open source JMS implementations. Therefore, FJM can be used in many innovative or mission critical cluster applications, such as massively multiplayer virtual worlds or military simulator.
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    The experience of using Java-based message-oriented middleware to build a distributed training simulator
    (2002)
    Chiao, HT
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    Lin, CH
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    Liang, KC
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    Yuan, SM
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    資訊工程學系
    This paper presents a prototype of a distributed training simulator for a surface-to-air missile system. Since the system requirement enforces us to choose open standard platform, and we think that Java is matured enough to offer acceptable performance and reliability, we decide to implement it by Java. Basically, this training simulator is a distributed interactive application, and lots of messages are exchanged within it. For the performance reason, we use an IP-multicast-based JMS implementation as the communication infrastructure for delivering time-critical events. In this paper, we present how to exploiting the capability, of the JMS publish/subscribe paradigm to implement this training simulator. Besides, we also perform a set of experiments to test and verify whether the training simulator can meet the system requirement. We think the experience of this paper is a good case study of using Java and message-oriented middleware to build message-intensive distributed systems.
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