The Blog (Posts about s3)

Model Checking: Formal Modeling and Verification

Nicolas Breton — Thu, 24 Apr 2025 16:18:44 GMT

Model Checking: Formal Modeling and Verification

Model Checking is a Formal Safety Verification method in which tools are used to analyze a model of a system in order to verify if it respects some safety properties. The analysis is performed by exploring every possible evolution trace of the system¹, verifying that the properties hold on these traces.

Back-to-back Testing

Anaïs Guignard, Julien Niguez, Nicolas Breton, Vincent Pouzol — Tue, 08 Nov 2022 10:21:44 GMT

Back-to-back testing (B2BT) techniques are used to verify that two products of a software development process are equivalent. By running the two products "back to back" on a set of test cases, it is verified that they produce the same output. If the scenarios are chosen carefully and the two runs produce the same results, it can be inferred that the two products are equivalent with some level of confidence.

Multi-Agent Smart Solver (MASS)

Vincent Pouzol — Thu, 04 Mar 2021 23:00:00 GMT

Systerel introduces the latest member in Systerel Smart Solver family: Multi-Agent Smart Solver (MASS). MASS significantly reduces proof wall clock time for the user, using extensible computing clusters.

S3 Formal Verification Solution — Instanciated Systems (4/4)

Nicolas Breton — Thu, 19 Dec 2019 09:44:53 GMT

Some systems are constructed by instantiating some generic design patterns on a collection of items (i.e. data). In the railway industry, the most widespread use of this mechanism is found for IXL, and to a lesser extend track-side ERTMS and CBTC systems.

While the overall structure of the S3 solutions dedicated to these kind of systems is not very different from that of the "standard" solutions described in the post about S3 workflow, they still admit some specificities. This section follows the structure of the aforementioned post and address these specificities.

This section will focus on IXL systems, but most of it could be adapted to other instantiated systems.

S3 Formal Verification Solution — Workflows (3/4)

Nicolas Breton — Wed, 18 Dec 2019 09:44:53 GMT

This post gives a generic description of the S3-based formal safety verification workflows. It starts with a short description of typical safety critical system development processes used in the industry. The two next section gives respectively a brief introduction to the S3 Modeling Languages, and a description of the development of the Safety Specification against which the system is to be verified. The rest of the section presents the S3 workflows together with the architecture and techniques used to ensure the trustworthiness of the solution.

S3 Formal Verification Solution — Introduction (2/4)

Nicolas Breton — Tue, 17 Dec 2019 09:44:53 GMT

Introduction

The ever-rising use of software-based systems to fulfill safety-critical missions calls for methods to ensure the adequacy of these systems to their missions. Most industrial sectors have brought an answer in the form of standards such as EN-50128 for railways, DO-178C for aviation, ISO-26262 for automotive, or more generally IEC-61508 for critical systems. All these standards have in common the central role given to test-based validation techniques. However, alternate and usually complementary techniques, grouped under the banner of "Formal Methods", are gaining increasing attention for the development and validation of these systems. In particular, the "Model Checking" technique has seen the multiplication of its application fields in the last decade.

S3 Formal Verification — Executive Summary (1/4)

Nicolas Breton — Mon, 16 Dec 2019 09:44:53 GMT

Formal Verification is the act of mathematically proving that a system respects some properties under a number of hypotheses. When such a property is proved to hold, it means that it is impossible to find an input scenario satisfying the hypotheses in which the system would falsify this property.

Systerel Smart Solver (S3) is a formal verification solution able to perform a proof of the safety of a critical system after its design (i.e. a posteriori). This solution, combining a specialized modeling language (HLL) with a SAT-based symbolic model checker, has shown to be particularly efficient in handling industrial-size critical systems coming from various domains such as railways or avionics.