Grids aim at exploiting synergies that result from cooperation of autonomous distributed entities. The synergies that result from grid cooperation include the sharing, exchange, selection, and aggregation of geographi...
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Grids aim at exploiting synergies that result from cooperation of autonomous distributed entities. The synergies that result from grid cooperation include the sharing, exchange, selection, and aggregation of geographically distributed resources such as computers, data bases, software, and scientific instruments for solving large-scale problems in science, engineering, and commerce. For this cooperation to be sustainable, participants need to have economic incentive. Therefore, "incentive" mechanisms should be considered as one of key design parameters of Grid architectures. We present an overview and status of an open source Grid toolkit, called Gridbus, whose architecture is fundamentally driven by the requirements of Grid economy. Gridbus technologies provide services for both computational and data grids that power the emerging eScience and eBusiness applications.
This paper describes an online control framework to design self-managing distributed computing systems that continually optimize their performance in response to changing computing demands and environmental conditions...
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ISBN:
(纸本)1581139896
This paper describes an online control framework to design self-managing distributed computing systems that continually optimize their performance in response to changing computing demands and environmental conditions. An on-line control technique is used in conjunction with predictive filters to tune the performance of individual system components based on their forecast behavior. In a distributed setting, a global controller is used to manage the interaction between components such that overall system requirements are satisfied.
Predicate abstraction is a major method for verification of software. However, the generation of the abstract Boolean program from the set of predicates and the original program suffers from an exponential number of t...
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Predicate abstraction is a major method for verification of software. However, the generation of the abstract Boolean program from the set of predicates and the original program suffers from an exponential number of theorem prover calls as well as from soundness issues. This paper presents a novel technique that uses an efficient SAT solver for generating the abstract transition relations of ANSI-C programs. The SAT-based approach computes a more precise and safe abstraction compared to existing predicate abstraction techniques.
Peer-to-peer (P2P) networks are generally considered to be free havens for pirated content, in particular with respect to music. We describe a solution for the problem of copyright infringement in P2P networks for mus...
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This paper describes TRAP/J, a software tool that enables new adaptable behavior to be added to existing Java applications transparently (that is, without modifying the application source code and without extending th...
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The paper introduces the concept of regression benchmarking as a variant of regression testing focused at detecting performance regressions. Applying the regression benchmarking in the area of middleware development, ...
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The paper introduces the concept of regression benchmarking as a variant of regression testing focused at detecting performance regressions. Applying the regression benchmarking in the area of middleware development, the paper explains how regression benchmarking differs from middleware benchmarking in general. On a real-world example of TAO, the paper shows why the existing benchmarks do not give results sufficient for regression benchmarking, and proposes techniques for detecting performance regressions using simple benchmarks.
The object constraint language (OCL) was introduced as part of the Unified Modeling Language (UML). Its main purpose is to make UML models more precise by providing a constraint language. For example, operation contra...
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The object constraint language (OCL) was introduced as part of the Unified Modeling Language (UML). Its main purpose is to make UML models more precise by providing a constraint language. For example, operation contracts and statechart guard conditions can be precisely defined using OCL. There has been an ongoing debate on the usefulness of using OCL in UML-based development, questioning whether the additional effort and formality were worth the benefit. This work presents the results of a controlled experiment that investigates the impact of using OCL on model comprehension and maintainability. Current results show that, once past an initial learning curve, significant benefits can be obtained by using OCL in combination with UML diagrams.
Many developers who could benefit from building and analysing formal models of their systems are deterred from doing so by the process algebra style input languages of formal modelling languages which they find diffic...
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Many developers who could benefit from building and analysing formal models of their systems are deterred from doing so by the process algebra style input languages of formal modelling languages which they find difficult to read and understand. This barrier to the adoption of formal modelling techniques can be significantly reduced if the process algebra is replaced with a graphical notation supported by a model generation tool. However, whilst having a diagrammatic base for the language appeals to the novice modeller, the diagrams can become cluttered for larger models. In this paper we address the issues of how to add hierarchical features to a graphical language without losing the fundamental benefits and appeal of having the graphical interface to the language. We illustrate these ideas using an existing formal modelling language
We concentrate on automated synthesis of multitolerant programs, i.e., programs that tolerate multiple classes of faults and provide a (possibly) different level of fault-tolerance to each class. We consider three lev...
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We concentrate on automated synthesis of multitolerant programs, i.e., programs that tolerate multiple classes of faults and provide a (possibly) different level of fault-tolerance to each class. We consider three levels of fault-tolerance: (1) failsafe, where in the presence of faults, the synthesized program guarantees safety, (2) nonmasking, where in the presence of faults, the synthesized program recovers to states from where its safety and liveness are satisfied, and (3) masking where in the presence of faults the synthesized program satisfies safety and recovers to states from where its safety and liveness are satisfied. We focus on the automated synthesis of finite-state multitolerant programs in high atomicity model where the program can read and write all its variables in an atomic step. We show that if one needs to add failsafe (respectively, nonmasking) fault-tolerance to one class of faults and masking fault-tolerance to another class of faults then such addition can be done in polynomial time in the state space of the fault-intolerant program. However, if one needs to add failsafe fault-tolerance to one class of faults and nonmasking fault-tolerance to another class of faults then the resulting problem is NP-complete. We find this result to be counterintuitive since adding failsafe and nonmasking fault-tolerance to the same class of faults (which is equivalent to adding masking fault-tolerance to that class of faults) can be done in polynomial time, whereas adding failsafe fault-tolerance to one class of faults and nonmasking fault-tolerance to a different class of faults is NP-complete.
Path probing is essential to maintain an efficient overlay network topology. However, the cost of complete probing can be as high as O(n/sup 2/), which is prohibitive in large-scale overlay networks. Recently we propo...
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Path probing is essential to maintain an efficient overlay network topology. However, the cost of complete probing can be as high as O(n/sup 2/), which is prohibitive in large-scale overlay networks. Recently we proposed a method that trades probing overhead for inference accuracy in sparse networks such as the Internet. The method uses physical path information to infer path quality for all of the n/spl times/(n-1) overlay paths, while actually probing only a subset of the paths. We propose and evaluate a distributed approach to implement this method. We describe a minimum diameter, link-stress bounded overlay spanning tree, which is used to collect and disseminate path quality information. All nodes in the tree collaborate to infer the quality of all paths. Simulation results show this approach can achieve a high-level of inference accuracy while reducing probing overhead and balancing link stress on the spanning tree.
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