BEval: A Plug-in to Extend Atelier B with Current Verification Technologies

This paper presents BEval, an extension of Atelier B to improve automation in the verification activities in the B method or Event-B. It combines a tool for managing and verifying software projects (Atelier B) and a model checker/animator (ProB) so that the verification conditions generated in the former are evaluated with the latter. In our experiments, the two main verification strategies (manual and automatic) showed significant improvement as ProB's evaluator proves complementary to Atelier B built-in provers. We conducted experiments with the B model of a micro-controller instruction set; several verification conditions, that we were not able to discharge automatically or manually with AtelierB's provers, were automatically verified using BEval.Comment: In Proceedings LAFM 2013, arXiv:1401.056

BDD-Driven First-Order Satisfiability Procedures (Extended Version)

Providing a high degree of automation to discharge proof obligations in (fragments of) first-order logic is a crucial activity in many verification efforts. Unfortunately, this is quite a difficult task. On the one hand, reasoning modulo ubiquitous theories (such as lists, arrays, and Presburger arithmetic) is essential. On the other hand, to effectively incorporate this theory specific reasoning in boolean manipulations requires a substantial work. In this paper, we propose a simple technique to cope with such difficult- ies whose aim is to check the validity of universally quantified formulae with arbitrary boolean structure modulo an equational theory. Our approach combines BDDs with refutation theorem proving. The former allows us to compactly represent the boolean structure of formulae, the latter to effectively mechanize the reasoning in equational theories. We report some experimental results on formulae extracted from software verification efforts which confirm both the flexibility and the viability of our approach

Agraphs: Definition, implementation and tools

Agraphs are a graph-based language representation, transformation and exchange format. In the same vein as XML, Agraphs form a general data representation mechanism that needs to be instantiated in different specific applications. In this paper, we present the Agraphs data structure, programming interface and related tools, identify their main features with respect to exchange format characteristics, and compare them to other existing exchange formats. These different features are illustrated on an instance of Agraphs for modular Petri nets

Explicit-Symbolic Modelling for Formal Verification

AbstractWe propose a model that combines explicit and symbolic representations in an explicit-symbolic formal verification model. Both explicit and symbolic models have been successfully used in the verification of finite state concurrent systems, such as complex sequential circuits and communication protocols. The proposed model aims to use explicit and symbolic techniques simultaneously to verify the same model and to make it possible to employ the most efficient technique to each aspect of the model. First, we formalize the explicit-symbolic model and show how it can be generated from a labeled state-transition system. Then, we apply those ideas to systems described in the Verimag Intermediate Format and present the main algorithms for integrating the underlying models

haRVey: combining reasoners

We present the architecture of the oncoming version of the SMT (Satisfiability Modulo Theories) solver haRVey. haRVey checks the satisfiability of a formula written in a first-order language with interpreted symbols from various theories. Its new architecture is original, first in the sense that it is a combination of reasoners, rather than the traditional combination of decision procedures. Second, one of these reasoners is a full-featured first-order saturation-based prover. Finally, some of those reasoners in the combination may only be sporadically activated not using computer time when inactive. We believe those new features will contribute to the efficiency and expressivity of the new version of the tool

Distributing the workload in a lazy theorem prover

Abstract. Automated theorem proving consists in automatically (i.e. without any user interaction) discharging proof obligations which arise when applying rigorous methodologies for designing critical software systems. Recent developements in the so-called lazy approach in the integration of Boolean satisfiability with decision procedures for decidable theories of first-order logic have provided new means to efficiently prove or refute such proof obligations. In this paper, we present the first (known) attempt to design a distributed version of lazy theorem proving on a network of computers so that the available processing power can be used more effectively and avoid that automated reasoning be the bottleneck of the application of formal methods. Experiments clearly show the viability and the benefits of the proposed approach

Verified Compilation and the B Method: A Proposal and a First Appraisal

AbstractThis paper investigates the application of the B method beyond the classical algorithmic level provided by the B0 sub-language, and presents refinements of B models at a level of precision equivalent to assembly language. We claim and justify that this extension provides a more reliable software development process as it bypasses two of the less trustable steps in the application of the B method: code synthesis and compilation. The results presented in the paper have a value as a proof of concept and may be used as a basis to establish an agenda for the development of an approach to build verifying compilers [Hoare, C. A. R., The verifying compiler, a grand challenge for computing research, in: VMCAI, 2005, pp. 78–78] based on the B method

Applying SMT Solvers to the Test Template Framework

The Test Template Framework (TTF) is a model-based testing method for the Z notation. In the TTF, test cases are generated from test specifications, which are predicates written in Z. In turn, the Z notation is based on first-order logic with equality and Zermelo-Fraenkel set theory. In this way, a test case is a witness satisfying a formula in that theory. Satisfiability Modulo Theory (SMT) solvers are software tools that decide the satisfiability of arbitrary formulas in a large number of built-in logical theories and their combination. In this paper, we present the first results of applying two SMT solvers, Yices and CVC3, as the engines to find test cases from TTF's test specifications. In doing so, shallow embeddings of a significant portion of the Z notation into the input languages of Yices and CVC3 are provided, given that they do not directly support Zermelo-Fraenkel set theory as defined in Z. Finally, the results of applying these embeddings to a number of test specifications of eight cases studies are analysed.Comment: In Proceedings MBT 2012, arXiv:1202.582