Utility computing has been anticipated to be the next generation of computing usage. Users have the freedom to easily switch to any commercial computing service to complete jobs whenever the need arises and simply pay...
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Mobility management is an important issue for publish/subscribe systems to support mobile clients. The objectives of mobility management for publish / subscribe are to achieve short handoff delay and low message overh...
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Service-Oriented Architectures provide integration of interoperability for independent and loosely coupled services. Web services and the associated new standards such as WSRF are frequently used to realise such Servi...
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ISBN:
(纸本)9780769530642
Service-Oriented Architectures provide integration of interoperability for independent and loosely coupled services. Web services and the associated new standards such as WSRF are frequently used to realise such Service-Oriented Architectures. In such systems, autonomic principles of self-configuration, self-optimisation, self-healing and self-adapting are desirable to ease management and improve robustness. In this paper we focus on the extension of the self management and autonomic behaviour of a WSRF container connected by a structured P2P overlay network to monitor and rectify its QoS to satisfy its SLAs. The SLA plays an important role during two distinct phases in the life-cycle of a WSRF container Firstly during service deployment when services are assigned to containers in such a way as to minimise the threat of SLA violations, and secondly during maintenance when violations are detected and services are migrated to other containers to preserve QoS. In addition, as the architecture has been designed and built using standardised modem technologies and with high levels of transparency, conventional web services can be deployed with the addition of a SLA specification.
Data gathering is a major function of many applications in wireless sensor networks (WSNs). The most important issue in designing a data gathering algorithm is how to save energy of sensor nodes while meeting the requ...
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ISBN:
(纸本)9781424403523
Data gathering is a major function of many applications in wireless sensor networks (WSNs). The most important issue in designing a data gathering algorithm is how to save energy of sensor nodes while meeting the requirement of applications/users such as sensing area coverage. In this paper, we propose a novel hierarchical clustering protocol for long-lived sensor network. EAP achieves a good performance in terms of lifetime by minimizing energy consumption for in-network communications and balancing the energy load among all nodes. EAP introduces a new clustering parameter for cluster head election, which can better handle the heterogeneous energy capacities. Furthermore, it also introduces a simple but efficient approach, namely intra-cluster coverage to cope with the area coverage problem. We evaluate the performance of the proposed protocol using a simple temperature sensing application. Simulation results show that our protocol significantly outperforms LEACH and HEED in terms of network lifetime and the amount of data gathered.
Component-based business-critical systems evolve during their life cycle in order to meet changing requirements or to improve quality properties. At the same time, maintaining continuous availability of services is an...
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Component-based business-critical systems evolve during their life cycle in order to meet changing requirements or to improve quality properties. At the same time, maintaining continuous availability of services is an issue with increasing importance for these systems. Runtime reconfiguration supports evolution of systems while maintaining availability of services they provide. In this paper, we present a new approach to runtime reconfiguration of component-based systems, which aims at optimising availability of requested services during reconfiguration. For a particular reconfiguration request, we analyse relevant scenarios based on the usage model of the system and exploit the component protocol information. Considering varying number of requests for a service at different points in time as well as the priority of each service, we compute minimal runtime dependency graphs among component instances and thus the maximal possible availability of services provided by the system. Finally, we sketch the system architecture for evaluating our approach.
This paper examines software designs produced by students nearing completion of their Computer science degrees. The results of this multi-national, multi institutional experiment present some interesting implications ...
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ISBN:
(纸本)9781595932594
This paper examines software designs produced by students nearing completion of their Computer science degrees. The results of this multi-national, multi institutional experiment present some interesting implications for educators. Copyright 2006 ACM.
Random Testing (RT) is a fundamental technique of software testing. Adaptive Random Testing (ART) has recently been developed as an enhancement of RT that has better fault detection effectiveness. Several methods (alg...
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This paper is part of an ongoing series of projects in which we are investigating "threshold concepts": concepts that, among other things, transforms the way a student looks as the discipline and are often t...
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ISBN:
(纸本)9781595938411
This paper is part of an ongoing series of projects in which we are investigating "threshold concepts": concepts that, among other things, transforms the way a student looks as the discipline and are often troublesome to learn. The word "threshold" might imply that students cross the threshold in a single "aha" moment, but often they seem to take longer. Meyer and Land introduce the term "liminal space" for the transitional period between beginning to learn a concept and fully mastering it. Based on in-depth interviews with graduating seniors, we found that the liminal space can provide a useful metaphor for the concept learning process. In addition to observing the standard features of liminal spaces, we have identified some that may be specific to computing, specifically those relating to levels of abstraction. Copyright 2007 ACM.
Recently SQL Injection Attack (SIA) has become a major threat to Web applications. Via carefully crafted user input, attackers can expose or manipulate the back-end database of a Web application. This paper proposes t...
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Utility computing has been anticipated to be the next generation of computing usage. Users have the freedom to easily switch to any commercial computing service to complete jobs whenever the need arises and simply pay...
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Utility computing has been anticipated to be the next generation of computing usage. Users have the freedom to easily switch to any commercial computing service to complete jobs whenever the need arises and simply pay only on usage, without any investment costs. A commercial computing service however has certain objectives or goals that it aims to achieve. In this paper, we identify three essential objectives for a commercial computing service: (i) meet SLA, (ii) maintain reliability, and (iii) earn profit. This leads to the problem of whether a resource management policy implemented in the commercial computing service is able to meet the required objectives or not. So, we also develop two evaluation methods that are simple and intuitive: (i) separate and (ii) integrated risk analysis to analyze the effectiveness of resource management policies in achieving the required objectives. Evaluation results based on five policies successfully demonstrate the applicability of separate and integrated risk analysis to assess policies in terms of the required objectives.
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