With society's increasing dependence on software, the issue of software quality is becoming more prominent. The term quality of service (QoS) has been used in conjunction with software to cover a broad range of ch...
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With society's increasing dependence on software, the issue of software quality is becoming more prominent. The term quality of service (QoS) has been used in conjunction with software to cover a broad range of characteristics, such as dependability, responsiveness, security, etc. Historically, the technical challenge of achieving a desired QoS in conditions of limited resources (e.g., finite computing power, memory capacity, communication bandwidth) was primarily relegated to the specialized domain of real-time and embedded software systems, that is, systems involved in continuous and timely interaction with the physical world. The "mainstream7" view and dominant software design philosophy are still based on the flawed premise that software should be developed without any considerations given to the characteristics and limitations of the hardware and software platforms that give it life. The important and useful principle of platform independence is being tragically misinterpreted as implying platform ignorance.
Recent years have witnessed the emergence and rapid growth of distributedservice infrastructures such as mobile ad hoc networks, P2P, PlanetLab and Grids. In such distributed infrastructures, an entity needs to utili...
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ISBN:
(纸本)9780769531328
Recent years have witnessed the emergence and rapid growth of distributedservice infrastructures such as mobile ad hoc networks, P2P, PlanetLab and Grids. In such distributed infrastructures, an entity needs to utilize the services provided by other entities or the infrastructures, where trust is an important factor. There exists a gap between current trust research focusing limitedly on specific applications and a systematic, adaptable and customizable trust framework. The first limitation of current research is the lack of characterizing service-specific trust features. The second limitation lies in the restricted evaluation formulae of trust values. The trust value formulae are usually drawn from a particular mathematical model and may not satisfy some desirable properties. The third limitation is the lack of flexibility and adaptability of trust models. In this paper a comprehensive trust model is presented to address these limitations and provide a trust-based environment for distributedservice infrastructures. Our simulation results demonstrate the robustness of the trust model against various attacks.
Building middleware for distributed applications is a complex task, mixing antagonistic concerns: heterogeneity, performance, reliability, quality of services. Optimization and fine-tuning of middleware for a particul...
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ISBN:
(纸本)9780769531328
Building middleware for distributed applications is a complex task, mixing antagonistic concerns: heterogeneity, performance, reliability, quality of services. Optimization and fine-tuning of middleware for a particular application is even a harder task, usually done manually or through complex design patterns. The advent of "schizophrenic" middleware which separates concerns between distribution model, communication protocols, and their implementation by refining the definition and role of "personalities" brought some elements to solve this problem by enabling full tailoring of the middleware by the developer. In this paper we extend this approach to full automation by generating middleware from an architectural model of the system expressed in a modeling language. This enables precise tuning and configuration of the middleware by generating exactly the required code, prior to runtime. We finally show how this approach fits the requirements of high-integrity or real-timedistributed systems.
Effective resource management for distributedreal-time embedded (DRE) systems is hard due to their unique characteristics, including (1) constraints in multiple resources and (2) highly fluctuating resource availabil...
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ISBN:
(纸本)9780769531328
Effective resource management for distributedreal-time embedded (DRE) systems is hard due to their unique characteristics, including (1) constraints in multiple resources and (2) highly fluctuating resource availability and input workload. DRE systems can benefit from a middleware framework that enables adaptive resource management algorithms to ensure application QoS requirements are met. This paper identifies key challenges in designing and extending resource allocation algorithms for DRE systems. We present an empirical study of bin-packing algorithms enhanced to meet these challenges. Our analysis identifies input application patterns that help generate appropriate heuristics for using these algorithms effectively in DRE systems.
distributed event-based systems (DEBS) are gaining increasing attention in new application areas such as transport information monitoring, event-driven supply-chain management and ubiquitous sensor-rich environments. ...
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ISBN:
(纸本)9780769531328
distributed event-based systems (DEBS) are gaining increasing attention in new application areas such as transport information monitoring, event-driven supply-chain management and ubiquitous sensor-rich environments. However, as DEBS increasingly enter the enterprise and commercial domains, performance and quality of service issues are becoming a major concern. While numerous approaches to performance modeling and evaluation of conventional request/reply-based distributed systems are available in the literature, no general approach exists for DEBS. This paper is the first to provide a comprehensive methodology for workload characterization and performance modeling of DEBS. A workload model of a generic DEBS is developed and operational analysis techniques are used to characterize the system traffic and derive an approximation for the mean event delivery latency. Following this, a modeling technique is presented that can be used for accurate performance prediction. The paper is concluded with a case study of a real life system demonstrating the effectiveness and practicality of the proposed approach.
Several real-time executable software specification languages and techniques exist. However, there are aspects among these languages that are preventing these languages from being widely accepted and adopted. The pape...
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ISBN:
(纸本)9780769531328
Several real-time executable software specification languages and techniques exist. However, there are aspects among these languages that are preventing these languages from being widely accepted and adopted. The paper identifies three key areas contributing to this non-acceptability. The paper also suggests future directions and advancements needed in the identified areas.
The real-time specification for Java extends the Java platform to support real-time processing and introduces a region-based memory model, called scoped memory, which side-steps the Java garbage collector. While scope...
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ISBN:
(纸本)9780769531328
The real-time specification for Java extends the Java platform to support real-time processing and introduces a region-based memory model, called scoped memory, which side-steps the Java garbage collector. While scoped memory succeeds in protecting real-time tasks from execution time jitter, practical experience points to shortcomings. This paper takes stock of the state of the art in memory management for RTSJ programs.
Recently, the application domains where the development of systems with temporal guarantees is needed have increased. The majority of such domains are dynamic environments where the classical design approach is no lon...
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ISBN:
(纸本)9780769531328
Recently, the application domains where the development of systems with temporal guarantees is needed have increased. The majority of such domains are dynamic environments where the classical design approach is no longer applicable since it is too pessimistic. Thus, new challenges arise to adapt the current methodologies used in different architectural levels to these new environments. New directions and paradigms are needed to allow combining functional flexibility and dynamism with temporal predictability. The current work addresses these new challenges through the exploration of the applicability of concepts from the serviceoriented paradigm to distributedreal-time systems. We propose a concrete system model based on a holistic time-triggered-based approach for design and configuration. Based on this model, we analyse the architectural entities required for two different architectural design approaches: static, when no reconfigurations at run-time are admitted, and dynamic, when these reconfigurations are possible. An exhaustive composition algorithm is also proposed.
Currently, the real-time Specification for Java (RTSJ) is silent on multiprocessor issues It attempts not to preclude multiprocessor implementations but provides no direct support. This paper discusses the issues that...
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Currently, the real-time Specification for Java (RTSJ) is silent on multiprocessor issues It attempts not to preclude multiprocessor implementations but provides no direct support. This paper discusses the issues that need to be addressed if the RTSJ is to be better defined for execution on a multiprocessor system. It proposes new dispatching and allocation models. Issues of cost enforcement, interrupts affinity and processor failure are covered.
Several approaches for scalable interest management (IM) within real-timedistributed virtual environments (DVEs) have been proposed based upon some division of the data-space in to disjoint volumes or cells. Any such...
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ISBN:
(纸本)9780769531328
Several approaches for scalable interest management (IM) within real-timedistributed virtual environments (DVEs) have been proposed based upon some division of the data-space in to disjoint volumes or cells. Any such approach, however, must implement some mechanism for propagating the query and update messages around the distributed system. The efficiency of this process can greatly effect the scalability of such systems. In this paper we evaluate an adaptive approach to this problem.
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