Incorporating faults and fault-tolerance into real-time networks: a graph-transformational approach

PhD ThesisThe introduction of fault tolerance into real-time systems presents particular challenges because of the price of redundancy and the added complexity of verification and validation on these redundant structures. This thesis brings structural and formal design techniques to bear on this problem. Verification of fault tolerance properties in such systems has only received limited attention. in particular the design methodologies are in their infancy. We propose a transformational design methodology, specific to a real-time systems architecture. We then reason about the compositional addition of fault tolerant components and templates of the derived designs. This requires that we show the existing axiomatic semantics for our chosen architecture sound with respect to a more constructive semantic model. The issues of presenting an operational model for a real-time architecture are discussed and a model is proposed. The extension of the existing semantics, to allow for faulty behaviour, is shown to preserve the existing semantic properties and the application of our methodology shown to be usable by a sizeable study. The contribution of this thesis is to define a transformational design methodology in which components can be extracted from a design and replaced by another component preserving functionality while providing fault tolerance. This approach requires the precise modelling of the faults we consider. the transformational method and verification of the transformed design with respect to faults.BAE Systems: EPSRC

Model-based dependability analysis : state-of-the-art, challenges and future outlook

Abstract: Over the past two decades, the study of model-based dependability analysis has gathered significant research interest. Different approaches have been developed to automate and address various limitations of classical dependability techniques to contend with the increasing complexity and challenges of modern safety-critical system. Two leading paradigms have emerged, one which constructs predictive system failure models from component failure models compositionally using the topology of the system. The other utilizes design models - typically state automata - to explore system behaviour through fault injection. This paper reviews a number of prominent techniques under these two paradigms, and provides an insight into their working mechanism, applicability, strengths and challenges, as well as recent developments within these fields. We also discuss the emerging trends on integrated approaches and advanced analysis capabilities. Lastly, we outline the future outlook for model-based dependability analysis

On Modelling and Analysis of Dynamic Reconfiguration of Dependable Real-Time Systems

This paper motivates the need for a formalism for the modelling and analysis of dynamic reconfiguration of dependable real-time systems. We present requirements that the formalism must meet, and use these to evaluate well established formalisms and two process algebras that we have been developing, namely, Webpi and CCSdp. A simple case study is developed to illustrate the modelling power of these two formalisms. The paper shows how Webpi and CCSdp represent a significant step forward in modelling adaptive and dependable real-time systems.Comment: Presented and published at DEPEND 201

A synthesis of logic and bio-inspired techniques in the design of dependable systems

Much of the development of model-based design and dependability analysis in the design of dependable systems, including software intensive systems, can be attributed to the application of advances in formal logic and its application to fault forecasting and verification of systems. In parallel, work on bio-inspired technologies has shown potential for the evolutionary design of engineering systems via automated exploration of potentially large design spaces. We have not yet seen the emergence of a design paradigm that effectively combines these two techniques, schematically founded on the two pillars of formal logic and biology, from the early stages of, and throughout, the design lifecycle. Such a design paradigm would apply these techniques synergistically and systematically to enable optimal refinement of new designs which can be driven effectively by dependability requirements. The paper sketches such a model-centric paradigm for the design of dependable systems, presented in the scope of the HiP-HOPS tool and technique, that brings these technologies together to realise their combined potential benefits. The paper begins by identifying current challenges in model-based safety assessment and then overviews the use of meta-heuristics at various stages of the design lifecycle covering topics that span from allocation of dependability requirements, through dependability analysis, to multi-objective optimisation of system architectures and maintenance schedules