Formal Methods in Industry

The application of formal methods in industry has progressed extensively over the past decade and the results are promising. But despite these achievements and it have been documented in numerous studies, it is still very common the skepticism about its usefulness and applicability. The goal of this paper is to show that its evolution over the past decade exceeds all previous processes and each time they do a better job to satisfy industrial needs. This is achieved by the description of some experiments and the result of various applications in industry and through an analyzing of the needs of companies that must be satisfy the research community in this field

Invariant discovery and refinement plans for formal modelling in Event-B

The continuous growth of complex systems makes the development of correct software increasingly challenging. In order to address this challenge, formal methods o er rigorous mathematical techniques to model and verify the correctness of systems. Refinement is one of these techniques. By allowing a developer to incrementally introduce design details, refinement provides a powerful mechanism for mastering the complexities that arise when formally modelling systems. Here the focus is on a posit-and-prove style of refinement, where a design is developed as a series of abstract models introduced via refinement steps. Each refinement step generates proof obligations which must be discharged in order to verify its correctness – typically requiring a user to understand the relationship between modelling and reasoning. This thesis focuses on techniques to aid refinement-based formal modelling, specifically, when a user requires guidance in order to overcome a failed refinement step. An integrated approach has been followed: combining the complementary strengths of bottomup theory formation, in which theories about domains are built based on basic background information; and top-down planning, in which meta-level reasoning is used to guide the search for correct models. On the theory formation perspective, we developed a technique for the automatic discovery of invariants. Refinement requires the definition of properties, called invariants, which relate to the design. Formulating correct and meaningful invariants can be tedious and a challenging task. A heuristic approach to the automatic discovery of invariants has been developed building upon simulation, proof-failure analysis and automated theory formation. This approach exploits the close interplay between modelling and reasoning in order to provide systematic guidance in tailoring the search for invariants for a given model. On the planning perspective, we propose a new technique called refinement plans. Refinement plans provide a basis for automatically generating modelling guidance when a step fails but is close to a known pattern of refinement. This technique combines both modelling and reasoning knowledge, and, contrary to traditional pattern techniques, allow the analysis of failure and partial matching. Moreover, when the guidance is only partially instantiated, and it is suitable, refinement plans provide specialised knowledge to further tailor the theory formation process in an attempt to fully instantiate the guidance. We also report on a series of experiments undertaken in order to evaluate the approaches and on the implementation of both techniques into prototype tools. We believe the techniques presented here allow the developer to focus on design decisions rather than on analysing low-level proof failures

A systematic approach to model-based engineering of cyber-physical systems of systems

PhD ThesisThis thesis describes and evaluates methods for the model-based engineering of Systems of Systems (SoSs) where constituents comprise both computational and physical elements typical of Cyber-Physical Systems (CPSs). Such Cyber-Physical Systems of Systems (CPSoSs) use sensors and actuators to link the digital and physical worlds, and are composed of operationally and managerially independent constituent systems that interact to deliver an emerging service on which reliance is placed. The engineering of CPSoSs requires a combination of techniques associated with both CPS engineering and SoS engineering. Model-based SoS engineering techniques address organisation and integration of diverse systems through the use of disciplined architectural frameworks and contractual modelling approaches. Advances in model-based CPS engineering address the additional challenges of integrating semantically heterogeneous models of discrete and continuous phenomena. This thesis combines these approaches to develop a coherent framework for the model-based engineering of CPSoSs. The proposed approach utilises architectural frameworks to aid in the development of rich abstract models of CPSoSs. This is accompanied by the specification of an automated transformation process to generate heterogeneous co-models based on the architectural description. Verification of the proposed engineering approach is undertaken by its application to a case study describing the control of trains over a section of rail network, in which the (cyber) behaviour of control infrastructure must be considered in conjunction with the (physical) dynamics of train movements. Using the proposed methods, the development of this CPSoS uses architectural descriptions to generate an executable model to enable the analysis of safety and efficiency implications of the implemented control logic. The utility of the approach is evaluated by consideration of the impact of the proposed techniques on advancing the suitability and maturity of baseline technologies for the engineering of CPSoS. It is concluded that the proposed architectural framework provides effective guidance for the production of rich architectural descriptions of CPSoSs, and that the conversion between architectural and executable models is viable for implementation in a suitable open tools framework