The ability to efficiently discover information using partial knowledge (for example keywords, attributes or ranges) is important in large, decentralized, resource sharing distributed environments such as computationa...
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ISBN:
(纸本)9780769519654
The ability to efficiently discover information using partial knowledge (for example keywords, attributes or ranges) is important in large, decentralized, resource sharing distributed environments such as computational grids and peer-to-peer (P2P) storage and retrieval systems. This paper presents a P2P information discovery system that supports flexible queries using partial keywords and wildcards, and range queries. It guarantees that all existing data elements that match a query are found with bounded costs in terms of number of messages and number of peers involved. The key innovation is a dimension reducing indexing scheme that effectively maps the multidimensional information space to physical peers. The design, implementation and experimental evaluation of the system are presented.
We previously developed a framework, Hydra, for adding formal semantics to a collection of UML diagrams that enable the automated derivation of formal language specifications for those diagrams. Recently, we have also...
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Path probing is essential to maintaining an efficient overlay network topology. However, the cost of a full-scale probing is as high as O(n/sup 2/), which is prohibitive in large-scale overlay networks. Several method...
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Path probing is essential to maintaining an efficient overlay network topology. However, the cost of a full-scale probing is as high as O(n/sup 2/), which is prohibitive in large-scale overlay networks. Several methods have been proposed to reduce probing overhead, although at a cost in terms of probing completeness. In this paper, an orthogonal solution is proposed that trades probing overhead for estimation accuracy in sparse networks such as the Internet. The proposed solution uses network-level path composition information (for example, as provided by a topology server) to infer path quality without full-scale probing. The inference metrics include latency, loss rate and available bandwidth. This approach is used to design several probing algorithms, which are evaluated through analysis and simulation. The results show that the proposed method can significantly reduce probing overhead while providing hounded quality estimations for all n /spl times/ (n - 1) overlay paths. The solution is well suited to medium-scale overlay networks in the Internet. In other environments, it can be combined with extant probing algorithms to further improve performance.
This paper describes the internal architecture and operation of an adaptable communication component called the MetaSocket. MetaSockets are created using Adaptive Java, a reflective extension to Java that enables a co...
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This paper describes the internal architecture and operation of an adaptable communication component called the MetaSocket. MetaSockets are created using Adaptive Java, a reflective extension to Java that enables a component's internal architecture and behavior to be adapted at run time in response to external stimuli. This paper describes how adaptive behavior is implemented in MetaSockets, as well as how MetaSockets interact with other adaptive components, such as decision makers and event mediators. Results of experiments on a mobile computing testbed demonstrate how MetaSockets respond to dynamic wireless channel conditions in order to improve the quality of interactive audio streams delivered to iPAQ handheld computers.
In this paper we focus on automated techniques to enhance the fault-tolerance of a nonmasking fault-tolerant program to masking. A masking program continually satisfies its specification even if faults occur. By contr...
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In this paper we focus on automated techniques to enhance the fault-tolerance of a nonmasking fault-tolerant program to masking. A masking program continually satisfies its specification even if faults occur. By contrast, a nonmasking program merely guarantees that after faults stop occurring, the program recovers to states from where it continually satisfies its specification. Until the recovery is complete, however a nonmasking program can violate its (safety) specification. Thus, the problem of enhancing fault-tolerance from nonmasking to masking requires that safety be added and recovery be preserved. We focus on this enhancement problem for high atomicity programs-where each process can read all variables-and for distributed programs-where restrictions are imposed on what processes can read and write. We present a sound and complete algorithm for high atomicity programs and a sound algorithm for distributed programs. We also argue that our algorithms are simpler than previous algorithms, where masking fault-tolerance is added to a fault-intolerant program. Hence, these algorithms can partially reap the benefits of automation when the cost of adding masking fault-tolerance to a fault-intolerant program is high. To illustrate these algorithms, we show how the masking fault-tolerant programs for triple modular redundancy and Byzantine agreement can be obtained by enhancing the fault-tolerance of the corresponding nonmasking versions. We also discuss how the derivation of these programs is simplified when we begin with a nonmasking fault-tolerant program.
In this paper we present the design, implementation and evaluation of the Grid-enabled Discover middleware substrate. The middleware substrate enables Grid infrastructure services provided by the Globus Toolkit (secur...
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The increasing complexity, heterogeneity and dynamism of networks, systems, services applications have made our computational/information infrastructure brittle, unmanageable and insecure. This has necessitated the in...
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The increasing complexity, heterogeneity and dynamism of networks, systems, services applications have made our computational/information infrastructure brittle, unmanageable and insecure. This has necessitated the investigation of a new paradigm for design, development and deployment based on strategies used by biological systems to deal with complexity, heterogeneity, and uncertainty, i.e. autonomic computing. This paper introduces the AutoMate project and describes its key components. The overall objective of AutoMate is to investigate key technologies to enable the development of autonomic grid applications that are context aware and are capable of self-configuring, self-composing, self-optimizing and self-adapting. Specifically, it will investigate the definition of autonomic components, the development of autonomic applications as dynamic composition of autonomic components, and the design of key enhancements to existing grid middleware and runtime services to support these applications.
At the 2001 IEEE International Conference on Data Mining in San Jose, California,on November 29 to December 2, 2001, there was a panel discussion on how datamining research meets practical development. One of the moti...
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