| Summary: | Performance-critical distributed systems, especially the distributed real-time and embedded (DRE) systems, have been proliferating in the past few decades. Designing and implementing DRE systems is significantly challenging due to various factors like the real-time reactive nature of the application, distribution of the application software components over a set of potentially resource constrained hosts and unpredictable network and environmental conditions. An important aspect of these systems is the necessity to guarantee a certain level of performance in terms of Quality-of-Service (QoS). Failure to meet QoS guarantees may result in severe consequences including mission failures. Current state-of-the-art uses ad-hoc methods to adaptively meet the design requirements for provision of QoS in DRE systems. However, these methods are not systematic enough to ensure system integrity or reusability.
In this thesis, we propose a model-based framework called the Dynamic QoS Modeling Environment (DQME) that provides a formal approach based on control-theory for satisfying QoS requirements. This framework provides design-time methodologies that facilitate an effective representation of QoS design and adaptation strategies along with the functional aspects of the system. These formal design-time adaptations are used to develop run-time adaptations. Code generators are provided for automatic synthesis of code that represents the behavior of the designed controllers and may be used in the low-level implementation frameworks.
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