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This chapter begins with an introduction to the main concepts of formal methods. Languages and tools for developing formal System modeis are also described, while the use of semi formal notations and their integration with formal methods is covered as well. At the end of the chapter, an overview of the current Status of formal methods in embedded System design is presented.

The approach presented in this book relies on the unification of System specification environments for developing electronic Systems that are formally proven to be correct (correct-by-construction Systems). The key concept conveyed is the formal proof of System properties, which is carried out at every phase of the co-design cycle. The main idea is to build fully functional System modeis that are formally proven to be correct, and based on them to produce automatically the hardware and the Software parts of the System. The approach presented relies on the combined use of UML and B language.

We present the adaptive cruise controller case study for B modelling and the Abstract: We P data model checking by RAVEN. Individual translations of B operations, data types, and invariants to the RAVEN Input Language are presented by the example of the case study.

The UML is a popular modelling notation that has a natural appeal to hardware and Software engineers and is adaptable through extension mechanisms. Formal (mathematical) modelling languages, on the other hand, are seen as difficult and costly to use and have achieved only limited use despite the benefits that they offer. In previous work, we have proposed an Integration of UML and the formal notation, B and provided an automatic translator that produces a B specification. The integrated modelling notation, UML-B, inherits from both UML and B but primarily, is a specialisation of the UML. To achieve this Integration we have specialised UML modelling elements via stereotypes, added tagged values to represent B modelling features and imposed constraints to ensure that UML-B modeis are translated into usable B. Here we describe ongoing work to define UML-B as a profile in accordance with the UML extensibility mechanisms.

The recognised deficiency in the level of empirical investigation of software engineering methods is particularly acute in the area of formal methods, where reports about their usefulness vary widely. We interviewed several formal methods users about the use of formal methods and their impact on various aspects of software engineering including the effects on the company, its products and its development processes as well as pragmatic issues such as scalability, understandability and tool support. The interviews are a first stage of empirical assessment. Future work will investigate some of the issues raised using formal experimentation and case studies.

Process assessment and process improvement are both very difficult tasks since we are either assessing or improving a concept rather than an object. A quality process is expected to produce quality products efficiently. Most of the existing models such as CMM, ISO 9001/9000-3 etc. intend to enhance the maturity or the quality of an organization with the assumption that a matured organization will put its processes in place which in turn will produce matured products. However, matured processes do not necessarily produce quality products [21, 6]. The primary reasons are: (i) In the process quality models, the relationship between the process quality and product quality is far from clear, and (ii) many of the process models take a monolithic view of the whole lifecycle process, and as a result, the idiosyncrasies of the individual processes do not receive proper attention. In this paper, we first define an internal process model in a formal manner. Next, we define a generic quality model whose scope covers all the development processes and most of the supporting processes associated with the development phase. The generic quality model is a parametric template and could be instantiated in a systematic manner to produce the quality model for any individual process. We then show such a customization for the formal specification process and use this customized model to formulate a GQM-based measurement plan for the same process. We then discuss how the generic model would be useful in process assessment and process improvement.

Event-B developments are mostly structured around the refinement relationship. This top-down development architecture enables system details to be gradually introduced into the formal model. However, this results in large models with monolithic structures. We develop a composition mechanism allowing to develop models bottom-up. In particular, our proposed mechanism works seamlessly with the existing refinement technique in Event-B. As a result we have built a formal development method that can take advantage of both top-down and bottom-up approaches. We prove the correctness of machine inclusion with refinement using the supporting Rodin platform.

Formal systems modelling offers a rigorous system-level analysis resulting in a precise and reliable specification. However, some issues remain: Modellers need to understand the requirements in order to formulate the models, formal verification may focus on safety properties rather than temporal behaviour, domain experts need to validate thefinal models to ensure they fit the needs of stakeholders. In this paper we discuss how the principles of Behaviour-Driven Development (BDD) can be applied to formal systems modelling and validation. We propose a process where manually authored scenarios are used initially to support the requirements and help the modeller.The same scenarios are used to verify behavioural properties of the model. The model is then mutated to automatically generate scenarios that have a more complete coverage than the manual ones. These automatically generated scenarios are used to animate the model in a final acceptance stage. For this acceptance stage, it is important that a domain expert decides whether or not the behaviour is useful.

We consider the failure detection and management function for engine control systems as an application domain where product line engineering is indicated. The need to develop a generic requirement set - for subsequent system instantiation - is complicated by the addition of the high levels of verification demanded by this safety-critical domain, subject to avionics industry standards. We present our case study experience in this area as a candidate methodology for the engineering, validation and verification of generic requirements using domain engineering and Formal Methods techniques and tools. For a defined class of systems, the case study produces a generic requirement set in UML and an example instantiation in tabular form. Domain analysis and engineering produce a model which is integrated with the formal specification/ verification method B by the use of our UML-B profile. The formal verification both of the generic requirement set, and of a simple system instance, is demonstrated using our U2B and ProB tools. This work is a demonstrator for a tool-supported method which will be an output of EU project RODIN. The method, based in the dominant UML standard, will exploit formal verification technology largely as a "black box" for this novel combination of product line, failure management and safety-critical engineering.

The emergence of the UML as a de facto standard for object-oriented modeling has been mirrored by the success of the B method as a practically useful formal modeling technique. The two notations have much to offer each other. The UML provides an accessible visualization of models facilitating communication of ideas but lacks formal precise semantics. B, on the other hand, has the precision to support animation and rigorous verification but requires significant effort in training to overcome the mathematical barrier that many practitioners perceive. We utilize a derivation of the B notation as an action and constraint language for the UML and define the semantics of UML entities via a translation into B. Through the UML-B profile we provide specializations of UML entities to support model refinement. The result is a formally precise variant of UML that can be used for refinement based, object-oriented behavioral modeling. The design of UML-B has been guided by industrial applications.