Computational Grids are emerging as a new infrastructure for Internet-based parallel and distributed computing. They enable the sharing, exchange, discovery, and aggregation of resources distributed across multiple ad...
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Computational Grids are emerging as a new infrastructure for Internet-based parallel and distributed computing. They enable the sharing, exchange, discovery, and aggregation of resources distributed across multiple administrative domains, organizations and enterprises. To accomplish this, Grids need infrastructure that supports various services: security, uniform access, resource management, scheduling, application composition, computational economy, and accounting. Although several initiatives are engaged in the development of Grid technologies, Grid accounting issues are yet to be addressed. To overcome this limitation, we propose a new infrastructure called GridBank that provides services for accounting. The support of computational economy and accounting services can lead to a self-regulated accountability in Grid computing. This paper presents requirements of Grid accounting and different economic models within which it can operate and proposes a Grid Accounting Services Architecture to meet them. The paper highlights implementation issues with a detailed discussion on the format for various records/databases that the GridBank needs to maintain. It also presents protocols for interaction between the GridBank and various components within Grid computing environments.
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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RDT is a graphical formal modeling language in which the modeler works by constructing diagrams of the processes in their model which they join together to form complete systems. Aside from the benefits which accrue a...
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RDT is a graphical formal modeling language in which the modeler works by constructing diagrams of the processes in their model which they join together to form complete systems. Aside from the benefits which accrue as a side effect of building a formal model of a proposed systems, these diagrammatic models can be useful as a means of communication between the development team and the users. However one of the greatest benefits of a formal model is that it can be subjected to rigorous examination to ensure that it satisfies properties required of the system. This paper describes the transformation used by the RDT toolset to generate Promela code (the input language of the SPIN model-checker) automatically from a model.
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.
Developing a business critical system can involve considerable difficulties. This paper describes part of a new methodology that tackles this problem using co-evolution of models and prototypes to strengthen the relat...
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Developing a business critical system can involve considerable difficulties. This paper describes part of a new methodology that tackles this problem using co-evolution of models and prototypes to strengthen the relationship between modelling and testing. We illustrate how different modelling frameworks, Promela/SPIN and B/ProB/AtellerB, can be used to implement this idea. As a way to reinforce integration between modelling and testing we use model-based tests and trace-driven model checking. As a result we were able to anticipate problems and guide the development of our software in a safer way, increasing our understanding of the system and its reliability.
The paper presents a model that is useful for developing resource allocation algorithms for distributed real-time systems that operate in dynamic environments. Interesting aspects of the model include dynamic environm...
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