31,646 research outputs found
Requirements Analysis of a Quad-Redundant Flight Control System
In this paper we detail our effort to formalize and prove requirements for
the Quad-redundant Flight Control System (QFCS) within NASA's Transport Class
Model (TCM). We use a compositional approach with assume-guarantee contracts
that correspond to the requirements for software components embedded in an AADL
system architecture model. This approach is designed to exploit the
verification effort and artifacts that are already part of typical software
verification processes in the avionics domain. Our approach is supported by an
AADL annex that allows specification of contracts along with a tool, called
AGREE, for performing compositional verification. The goal of this paper is to
show the benefits of a compositional verification approach applied to a
realistic avionics system and to demonstrate the effectiveness of the AGREE
tool in performing this analysis.Comment: Accepted to NASA Formal Methods 201
Formal Verification of Real-Time Function Blocks Using PVS
A critical step towards certifying safety-critical systems is to check their
conformance to hard real-time requirements. A promising way to achieve this is
by building the systems from pre-verified components and verifying their
correctness in a compositional manner. We previously reported a formal approach
to verifying function blocks (FBs) using tabular expressions and the PVS proof
assistant. By applying our approach to the IEC 61131-3 standard of Programmable
Logic Controllers (PLCs), we constructed a repository of precise specification
and reusable (proven) theorems of feasibility and correctness for FBs. However,
we previously did not apply our approach to verify FBs against timing
requirements, since IEC 61131-3 does not define composite FBs built from
timers. In this paper, based on our experience in the nuclear domain, we
conduct two realistic case studies, consisting of the software requirements and
the proposed FB implementations for two subsystems of an industrial control
system. The implementations are built from IEC 61131-3 FBs, including the
on-delay timer. We find issues during the verification process and suggest
solutions.Comment: In Proceedings ESSS 2015, arXiv:1506.0325
About the nature of Kansei information, from abstract to concrete
Designer’s expertise refers to the scientific fields of emotional design and kansei information. This paper aims to answer to a scientific major issue which is, how to formalize designer’s knowledge, rules, skills into kansei information systems. Kansei can be considered as a psycho-physiologic, perceptive, cognitive and affective process through a particular experience. Kansei oriented methods include various approaches which deal with semantics and emotions, and show the correlation with some design properties. Kansei words may include semantic, sensory, emotional descriptors, and also objects names and product attributes. Kansei levels of information can be seen on an axis going from abstract to concrete dimensions. Sociological value is the most abstract information positioned on this axis. Previous studies demonstrate the values the people aspire to drive their emotional reactions in front of particular semantics. This means that the value dimension should be considered in kansei studies. Through a chain of value-function-product attributes it is possible to enrich design generation and design evaluation processes. This paper describes some knowledge structures and formalisms we established according to this chain, which can be further used for implementing computer aided design tools dedicated to early design. These structures open to new formalisms which enable to integrate design information in a non-hierarchical way. The foreseen algorithmic implementation may be based on the association of ontologies and bag-of-words.AN
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
Verifying the Safety of a Flight-Critical System
This paper describes our work on demonstrating verification technologies on a
flight-critical system of realistic functionality, size, and complexity. Our
work targeted a commercial aircraft control system named Transport Class Model
(TCM), and involved several stages: formalizing and disambiguating requirements
in collaboration with do- main experts; processing models for their use by
formal verification tools; applying compositional techniques at the
architectural and component level to scale verification. Performed in the
context of a major NASA milestone, this study of formal verification in
practice is one of the most challenging that our group has performed, and it
took several person months to complete it. This paper describes the methodology
that we followed and the lessons that we learned.Comment: 17 pages, 5 figure
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