Abstract Control systems, protocols, and hardware design are among the most common applications of state-based formal methods, and yet the types of modeling and analysis they enable are also well-suited to problems in scientific computation, where quality, reproducibility, and productivity are growing concerns. We survey the challenges faced by developers of scientific software, characterize the nature of the programs they write, and offer some perspective on the role that state-based methods can play in scientific domains.
Abstract Relational algebra forms the semantic foundation in multiple domains, e.g., Alloy models, OCL constraints, UML metamodels, and SQL queries. Synthesis and repair techniques in such domains require an efficient procedure to generate (non-equivalent) expressions subject to relational constraints, e.g., the types of sets and relations, their cardinality, size of expressions, maximum arity of the intermediate expressions, etc. This paper introduces the first generator for relational expressions that are non-equivalent with respect to the semantics of relational algebra. We present the algorithms that define our generator, its embodiment based on the Alloy tool-set, and an experimental evaluation to show the effectiveness of its non-equivalent generation for a variety of problems with relational constraints.
Abstract Graph algorithms that involve complex conditions on subgraphs can be specified much easier, if the specification allows expressions in higher-order logic to be used. In this paper an extension of Abstract State Machines by such expressions is introduced and its usefulness is demonstrated by examples of computations on graphs, such as graph factoring and checking self-similarity. In a naïve way these high-level specifications can be refined using submachines for the evaluation of the higher-order expressions. We show that refinements can be obtained in an automatic way for well-defined fragments of higher-order logic that collapse to second-order, by means of which the naïve refinement is only necessary for second-order logic expressions.
Abstract This paper presents an evolution of an industrial proof support framework that integrates state-of-the-art technologies without compromising the existing tool qualification status. Third-party provers produce proof rules that may be applied by the legacy system and verified using a certified approach. This approach has been implemented in Atelier B, a formal-methods based IDE for the development of software components and for the modeling of systems.
Abstract Role-Based Access Control (RBAC) is a popular authorization model used to manage resource-access constraints in a wide range of systems. The standard RBAC framework adopts a static, state-independent approach to define the access rights to the system resources. It is often insufficient for correct implementation of the desired functionality and should be augmented with the dynamic, i.e., a state-dependant view on the access control. In this paper, we present a work in progress on creating a domain-specific language and the tool support for modelling and verification of dynamic RBAC. They support a tabular representation of the static RBAC constraints together with the graphical model of the scenarios and enable an automated translation of them into an Event-B model.
Abstract Scheduled Event-B (SEB) augments Event-B with a scheduling language to make the control flow in an Event-B model explicit and facilitate derivation of algorithmic structure in Event-B refinement. A concrete SEB model has a concrete algorithmic structure associated with it. Although this structure reduces the difficulty of code generation, there is still some gap between the model and executable code. This work formulates the translation of SEB models to a programming language called Dafny and proposes an approach in which a number of assertions are generated from the model that allows the verification of the generated code in a static program verifier.
This document presents a description of the European Rail Traffic Management System (ERTMS) case study. ERTMS is a system of standards for management and interoperation of signalling for railways by the European Union (EU). The case study focuses on the ERTMS Level 3 Hybrid principle, which accommodates different types of trains including ERTMS trains equiped with the Train Integrity Monitoring System (TIMS), ERTMS trains without TIMS, and non-ERTMS trains.