A Model–Based Design Methodology with Contracts to Enhance the Development Process of Safety–Critical Systems

International audienceIn this paper a new methodology to support the development process of safety-critical systems with contracts is described. The meta-model of Heterogeneous Rich Component (HRC) is extended to a Common System Meta-Model (CSM) that benefits from the semantic foundation of HRC and provides analysis techniques such as compatibility checks or refinement analyses. The idea of viewpoints, perspectives, and abstraction levels is discussed in detail to point out how the CSM supports separation of concerns. An example is presented to detail the transition concepts between models. From the example we conclude that our approach proves valuable and supports the development process

Contracts for Systems Design: Methodology and Application cases

Recently, contract based design has been proposed as an ”orthogonal” approach that can beapplied to all methodologies proposed so far to cope with the complexity of system design. Contract baseddesign provides a rigorous scaffolding for verification, analysis and abstraction/refinement. Companionreport RR-8759 proposes a unified treatment of the topic that can help in putting contract-based design in perspective.This paper complements RR-8759 by further discussing methodological aspects of system design withcontracts in perspective and presenting two application cases.The first application case illustrates the use of contracts in requirement engineering, an area of system designwhere formal methods were scarcely considered, yet are stringently needed. We focus in particular to thecritical design step by which sub-contracts are generated for suppliers from a set of different viewpoints(specified as contracts) on the global system. We also discuss important issues regarding certification inrequirement engineering, such as consistency, compatibility, and completeness of requirements.The second example is developed in the context of the Autosar methodology now widely advocated inthe automotive sector. We propose a contract framework to support schedulability analysis, a key step inAutosar methodology. Our aim differs from the many proposals for compositional schedulability analysisin that we aim at defining sub-contracts for suppliers, not just performing the analysis by parts—we knowfrom companion paper RR-8759 that sub-contracting to suppliers differs from a compositional analysis entirelyperformed by the OEM. We observe that the methodology advocated by Autosar is in contradiction withcontract based design in that some recommended design steps cannot be refinements. We show how tocircumvent this difficulty by precisely bounding the risk at system integration phase. Another feature ofthis application case is the combination of manual reasoning for local properties and use of the formalcontract algebra to lift a collection of local checks to a system wide analysis

Contracts for Systems Design: Theory

Aircrafts, trains, cars, plants, distributed telecommunication military or health care systems,and more, involve systems design as a critical step. Complexity has caused system design times and coststo go severely over budget so as to threaten the health of entire industrial sectors. Heuristic methods andstandard practices do not seem to scale with complexity so that novel design methods and tools based on astrong theoretical foundation are sorely needed. Model-based design as well as other methodologies suchas layered and compositional design have been used recently but a unified intellectual framework with acomplete design flow supported by formal tools is still lacking.Recently an “orthogonal” approach has been proposed that can be applied to all methodologies introducedthus far to provide a rigorous scaffolding for verification, analysis and abstraction/refinement: contractbaseddesign. Several results have been obtained in this domain but a unified treatment of the topic that canhelp in putting contract-based design in perspective is missing. This paper intends to provide such treatmentwhere contracts are precisely defined and characterized so that they can be used in design methodologiessuch as the ones mentioned above with no ambiguity. In addition, the paper provides an important linkbetween interface and contract theories to show similarities and correspondences.This paper is complemented by a companion paper where contract based design is illustrated throughuse cases

Contracts for System Design

Systems design has become a key challenge and differentiating factor over the last decades for system companies. Aircrafts, trains, cars, plants, distributed telecommunication military or health care systems, and more, involve systems design as a critical step. Complexity has caused system design times and costs to go severely over budget so as to threaten the health of entire industrial sectors. Heuristic methods and standard practices do not seem to scale with complexity so that novel design methods and tools based on a strong theoretical foundation are sorely needed. Model-based design as well as other methodologies such as layered and compositional design have been used recently but a unified intellectual framework with a complete design flow supported by formal tools is still lacking albeit some attempts at this framework such as Platform-based Design have been successfully deployed. Recently an "orthogonal" approach has been proposed that can be applied to all methodologies proposed thus far to provide a rigorous scaffolding for verification, analysis and abstraction/refinement: contractbased design. Several results have been obtained in this domain but a unified treatment of the topic that can help in putting contract-based design in perspective is still missing. This paper intends to provide such treatment where contracts are precisely defined and characterized so that they can be used in design methodologies such as the ones mentioned above with no ambiguity. In addition, the paper provides an important link between interfaces and contracts to show similarities and correspondences. Examples of the use of contracts in design are provided as well as in depth analysis of existing literature.Cet article fait le point sur le concept de contrat pour la conception de systèmes. Les contrats que nous proposons portent, non seulement sur des propriétés de typage de leurs interfaces, mais incluent une description abstraite de comportements. Nous proposons une méta-théorie, ou, si l'on veut, une théorie générique des contrats, qui permet le développement séparé de sous-systèmes. Nous montrons que cette méta-théorie se spécialise en l'une ou l'autre des théories connues

Compositional Timing Analysis of Real-Time Systems Based on Resource Segregation Abstraction

Part 5: ARAMIS Special SessionInternational audienceFor most embedded safety-critical systems not only the functional correctness is of importance, but they must provide their services also in a timely manner. Therefore, it is important to have rigorous analysis techniques for determining timing properties of such systems. The ever increasing complexity of such real-time systems calls for compositional analysis techniques, where timing properties of local systems are composed to infer timing properties of the overall system. In analytical timing analysis approaches the dynamic timing behavior of a system is characterized by mathematical formulas abstracting from the state-dependent behavior of the system. While these approaches scale well and also support compositional reasoning, the results often exhibit large over-approximations. Our approach for compositional timing analysis is based on ω-regular languages, which can be employed in automata-based model-checking frameworks. To tackle the scalability problem due to state-space explosion, we present a technique to abstract an application by means of its resource demands. The technique allows to carry out an analysis independently for each application that shall be deployed on the same platform using its granted resource supply. Integration of the applications on the platform can then be analyzed based on the different resource supplies without considering details of the applications

Contracts for Schedulability Analysis

International audienceIn this paper we propose a framework of Assume / Guarantee contracts for schedulability analysis. Unlike previous work addressing compositional scheduling analysis, our objective is to provide support for the OEM / supplier subcontracting relation. The adaptation of Assume / Guarantee contracts to schedulability analysis requires some care, due to the handling of conflicts caused by shared resources. We illustrate our framework in the context of Autosar methodology now popular in the automotive industry sector

Contracts for System Design

International audienceRecently, contract-based design has been proposed as an “orthogonal” approach that complements system design methodologies proposed so far to cope with the complexity of system design. Contract-based design provides a rigorous scaffolding for verification, analysis, abstraction/refinement, and even synthesis. A number of results have been obtained in this domain but a unified treatment of the topic that can help put contract-based design in perspective was missing. This monograph intends to provide such a treatment where contracts are precisely defined and characterized so that they can be used in design methodologies with no ambiguity. In particular, this monograph identifies the essence of complex system design using contracts through a mathematical “meta-theory”, where all the properties of the methodology are derived from a very abstract and generic notion of contract. We show that the meta-theory provides deep and illuminating links with existing contract and interface theories, as well as guidelines for designing new theories. Our study encompasses contracts for both software and systems, with emphasis on the latter. We illustrate the use of contracts with two examples: requirement engineering for a parking garage management, and the development of contracts for timing and scheduling in the context of the AUTOSAR methodology in use in the automotive sector

Smart Healthcare

Internet-of-Things and machine learning promise a new era for healthcare. The emergence of transformative technologies, such as Implantable and Wearable Medical Devices (IWMDs), has enabled collection and analysis of physiological signals from anyone anywhere anytime. Machine learning allows us to unearth patterns in these signals and make healthcare predictions in both daily and clinical situations. This broadens the reach of healthcare from conventional clinical contexts to pervasive everyday scenarios, from passive data collection to active decision-making. Despite the existence of a rich literature on IWMD-based and clinical healthcare systems, the fundamental challenges associated with design and implementation of smart healthcare systems have not been well-addressed. The main objectives of this article are to define a standard framework for smart healthcare aimed at both daily and clinical settings, investigate state-of-the-art smart healthcare systems and their constituent components, discuss various considerations and challenges that should be taken into account while designing smart healthcare systems, explain how existing studies have tackled these design challenges, and finally suggest some avenues for future research based on a set of open issues and challenges