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...s (e.g. scheduling analysis,sadaptation to ORB real-time services, object replicationsand faults detections, replicated and real-timescommunication mechanism, adaptation to ORB faulttolerant services)=-=[19]-=-. The integration of QoS servicessinto middleware has been identified as a future challengesfor the middleware infrastructures [16,11]. We havesbased our studies in some prototypes, where we havesadap...

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...atterns for composing component-based middleware [9,10], (2) applying reflective middleware [11] techniques to enable mechanisms within the component-based middleware to support different QoS aspects =-=[12]-=-, (3) configuring real-time aspects [6] within component middleware to support DRE systems, and (4) developing domain-specific modeling languages that provide design-time capabilities to deploy and co...

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...ements, monitor the provided QoS level and adapt to QoS changes. This approach is also characterised by its distributed nature and its applicationoriented management. Reflective architectures at the middleware level have also been investigated as an effective means of offering flexibility and support for application configuration. Reflection is particularly attractive because of its inherent property of self-awareness. Reflection allows for the adaptations of core software and hardware without explicit intervention by application or end user, an important characteristic of autonomic behaviour [13]. Some of the benefits that accrue from the adoption of reflective middleware techniques for QoS-enabled component-based techniques relate to the enhanced adaptation at various levels. More specifically, optimal communications mechanisms can be selected and runtime components can be configured dynamically. Blair et al [14] developed a reflective architecture where configuration is achieved by introducing or removing management components on demand. At a higher level, reflection promotes also a policy-driven approach to QoS management. A policy for management can be inspected and adapted dynami...

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...nt of custom non-functional services and associated policies. [KC99, WKS00] propose solutions for the automatic reconfiguration of software components to provide fault-tolerant and real-time support: =-=[WKS00]-=- introduces the QoS Container Adaptor concept. This type of container is based on scheduling and QoS services to provide QoS support to business components. The objective is to provide support for the...

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...s, each of which does a few tasks, and composition of these tasks can make the proposed aims of the determined middleware. Activation of components must occur in real-time, which means that component initialization must not become a bottleneck. Thus, on-demand linking/unlinking mechanisms are necessary to (re)configure component implementations dynamically. The lifecycle for linking/unlinking of these components must be optimized using reflective middleware techniques to minimize footprint, prolong battery life, maximize extensibility, and meet key application QoS requirements more adaptively [25]. Thus, we need an additional feature for our model: reflection, which defines the rules for cooperating among components to do the whole task. Clearly, we will need operations to generate and delete component(s), and (un)establish connections among components to reach a complete model. Reflection refers to the ability of a system to reason about and act upon itself. More specifically, a reflective system is one that provides a representation of its own behavior which is amenable to inspection and 2 adaptation, and is casually connected to the underlying behavior it describes. Casually-connect...

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... applied to optimizing middleware for component-based systems under two categories: 1. Component Middleware Research on optimizing component middleware techniques have relied on reflection techniques =-=[61]-=- to optimize away the overhead of invocations. Approaches to optimizations have focused on selecting optimal communication mechnanisms, managing QoS properties of component using the containers and dy...