The composition of Event-B models

The transition from classical B [2] to the Event-B language and method [3] has seen the removal of some forms of model structuring and composition, with the intention of reinventing them in future. This work contributes to thatreinvention. Inspired by a proposed method for state-based decomposition and refinement [5] of an Event-B model, we propose a familiar parallel event composition (over disjoint state variable lists), and the less familiar event fusion (over intersecting state variable lists). A brief motivation is provided for these and other forms of composition of models, in terms of feature-based modelling. We show that model consistency is preserved under such compositions. More significantly we show that model composition preserves refinement

Real-Time DSP-Free 100Gbit/s/λ PAM-4 Fiber Access Link using EML and Direct Detection

A 100 Gbit/s/ λ PAM-4 fiber link with an optical budget of 30 dB and 20 km fiber reach is achieved in real time experiments. This is compliant with class A (20 dB) point to point (PtP) applications as mobile fronthaul for example, and with class N1 (29 dB) point to multipoint (PtMP) for residential market. We used an integrated externally modulated laser, an analog pre-equalizer, an optical booster amplifier and/or non-filtered preamplifier and direct detection without any digital signal processing (whether real-time or offline)

Genome-wide association analyses identify new Brugada syndrome risk loci and highlight a new mechanism of sodium channel regulation in disease susceptibility

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel NaV1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on NaV1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings

Automatic Construction of Validated B Components from Structured Developments

Decomposition and refinement provide a way to master the complexity of system specification and development. Decomposition allows us to describe a complex system in term of simpler and more understandable components and in terms of the interactions between these components. Refinement/Abstraction allows us to use more general specifications, which should also be more understandable, and which can be gradually made more precise. Combining decomposition and refinement offers a very powerful tool to build specifications. This process results in a structured object which describes both the final specification and its elaboration in term of interaction and refinement. Nevertheless the result remains intrinsically a complex object. The next step consists in developing tools to represent, to manipulate and to reason about such structured objects. The aim of this paper is to propose such a tool in the framework of the B method. By exploiting the B theory, and as far as possible without changing the method, we propose three algorithms to extract validated B components, using properties underlying the structure of developments. These new components can be exploited to extend a structured development, for instance to validate new properties

Bending sensors based on fiber Bragg gratings: The key role of the mean effective index

In this article we show that the Bragg wavelength variation induced by a curvature in the fiber Bragg grating is related to both the variation of the effective index and the variation of the coupling coefficient of counter-propagating modes. The weighting coefficient between the two variables is the mean effective index of the grating. The two effects act in opposition as proved both by our model and by our experimental observations. This work can be used to design strain sensors insensitive to bending, or, on the contrary, bending sensors insensitive to strain

Fault attack vulnerability assessment of binary code

International audienceFault attacks are a major threat requiring to protect applications. We present a method and a set of metrics, implemented in a framework combining formal methods, dynamic and static analyses to evaluate the robustness of a binary code against fault attacks. The framework models the vulnerabilities detection as formal equivalence-checking problems that are solved by a SMT solver. It can support transient fault models targeting both data and code. Its application to programs hardened at source level shows its benefits for comparing different hardened versions, compilers and their optimizations, and for analyzing the sources of vulnerability

Adaptable translator of B specifications to embedded C programs

Abstract. This paper presents the results of the RNTL BOM project, which aimed to develop an approach to generate efficient code from B formal developments. The target domain is smart card applications, in which memory and code size is an important factor. The results detailed in this paper are a new architecture of the translation process, a way to adapt the B0 language in order to include types of the target language and a set of validated optimizations. An assessment of the proposed approach is given through a case study, relative to the development of a Java Card Virtual Machine environment. Keywords. Code generation, embedded systems, B method, smart cards