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Formalization and Validation of Safety-Critical Requirements
The validation of requirements is a fundamental step in the development
process of safety-critical systems. In safety critical applications such as
aerospace, avionics and railways, the use of formal methods is of paramount
importance both for requirements and for design validation. Nevertheless, while
for the verification of the design, many formal techniques have been conceived
and applied, the research on formal methods for requirements validation is not
yet mature. The main obstacles are that, on the one hand, the correctness of
requirements is not formally defined; on the other hand that the formalization
and the validation of the requirements usually demands a strong involvement of
domain experts. We report on a methodology and a series of techniques that we
developed for the formalization and validation of high-level requirements for
safety-critical applications. The main ingredients are a very expressive formal
language and automatic satisfiability procedures. The language combines
first-order, temporal, and hybrid logic. The satisfiability procedures are
based on model checking and satisfiability modulo theory. We applied this
technology within an industrial project to the validation of railways
requirements
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Using formal methods to support testing
Formal methods and testing are two important approaches that assist in the development of high quality software. While traditionally these approaches have been seen as rivals, in recent
years a new consensus has developed in which they are seen as complementary. This article reviews the state of the art regarding ways in which the presence of a formal specification can be used to assist testing
Syntactic Abstraction of B Models to Generate Tests
In a model-based testing approach as well as for the verification of
properties, B models provide an interesting solution. However, for industrial
applications, the size of their state space often makes them hard to handle. To
reduce the amount of states, an abstraction function can be used, often
combining state variable elimination and domain abstractions of the remaining
variables. This paper complements previous results, based on domain abstraction
for test generation, by adding a preliminary syntactic abstraction phase, based
on variable elimination. We define a syntactic transformation that suppresses
some variables from a B event model, in addition to a method that chooses
relevant variables according to a test purpose. We propose two methods to
compute an abstraction A of an initial model M. The first one computes A as a
simulation of M, and the second one computes A as a bisimulation of M. The
abstraction process produces a finite state system. We apply this abstraction
computation to a Model Based Testing process.Comment: Tests and Proofs 2010, Malaga : Spain (2010
Development of a framework for automated systematic testing of safety-critical embedded systems
“This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder." “Copyright IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.”In this paper we introduce the development of a framework for testing safety-critical embedded systems based on the concepts of model-based testing. In model-based testing the test cases are derived from a model of the system under test. In our approach the model is an automaton model that is automatically extracted from the C-source code of the system under test. Beside random test data generation the test case generation uses formal methods, in detail model checking techniques. To find appropriate test cases we use the requirements defined in the system specification. To cover further execution paths we developed an additional, to our best knowledge, novel method based on special structural coverage criteria. We present preliminary results on the model extraction using a concrete industrial case study from the automotive domain
Symmetry Reduction Enables Model Checking of More Complex Emergent Behaviours of Swarm Navigation Algorithms
The emergent global behaviours of robotic swarms are important to achieve
their navigation task goals. These emergent behaviours can be verified to
assess their correctness, through techniques like model checking. Model
checking exhaustively explores all possible behaviours, based on a discrete
model of the system, such as a swarm in a grid. A common problem in model
checking is the state-space explosion that arises when the states of the model
are numerous. We propose a novel implementation of symmetry reduction, in the
form of encoding navigation algorithms relatively with respect to a reference,
based on the symmetrical properties of swarms in grids. We applied the relative
encoding to a swarm navigation algorithm, Alpha, modelled for the NuSMV model
checker. A comparison of the state-space and verification results with an
absolute (or global) and a relative encoding of the Alpha algorithm highlights
the advantages of our approach, allowing model checking larger grid sizes and
number of robots, and consequently, verifying more complex emergent behaviours.
For example, a property was verified for a grid with 3 robots and a maximum
allowed size of 8x8 cells in a global encoding, whereas this size was increased
to 16x16 using a relative encoding. Also, the time to verify a property for a
swarm of 3 robots in a 6x6 grid was reduced from almost 10 hours to only 7
minutes. Our approach is transferable to other swarm navigation algorithms.Comment: Accepted for presentation in Towards Autonomous Robotic Systems
(TAROS) 2015, Liverpool, U
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