Deriving safety cases for hierarchical structure in model-based development

Model-based development and automated code generation are increasingly used for actual production code, in particular in mathematical and engineering domains. However, since code generators are typically not qualified, there is no guarantee that their output satisfies the system requirements, or is even safe. Here we present an approach to systematically derive safety cases that argue along the hierarchical structure in model-based development. The safety cases are constructed mechanically using a formal analysis, based on automated theorem proving, of the automatically generated code. The analysis recovers the model structure and component hierarchy from the code, providing independent assurance of both code and model. It identifies how the given system safety requirements are broken down into component requirements, and where they are ultimately established, thus establishing a hierarchy of requirements that is aligned with the hierarchical model structure. The derived safety cases reflect the results of the analysis, and provide a high-level argument that traces the requirements on the model via the inferred model structure to the code. We illustrate our approach on flight code generated from hierarchical Simulink models by Real-Time Worksho

Analysing Regional Sustainability Through a Systemic Approach: The Lombardy Case Study

The intrinsic complexity of the sustainability concept challenges research towards more sophisticated ways to model and assess the dimensions underlying it. However, currently adopted modelling techniques and indicators frameworks are not able to give an integrated assessment through the different components of sustainability, providing incomplete visuals of the reality that they aim to catch. This paper tries to assess how the INSURE methodology can provide a contribution in the analysis of sustainability through indicator frameworks, describing its application to the Lombardy region (Italy). Developed on the course of a 6th European Framework Program – financed project to measure sustainability in the European regions, the methodology provides two distinct sustainability representations, based on a quantitative “top-down” System Dynamics model and on a qualitative “bottom-up” System Thinking approach. The models are then linked to a hierarchical indicator framework setting policy priorities. The overall objective is thus to create a set of regional indicators, adapting the models of regional sustainability to different policy agendas. The purpose of the paper is twofold: defining a new approach to sustainability appraisal, and assessing how the Region is holistically behaving towards sustainable development. Starting from a basis analysis of the main shortcomings highlighted by the use of most adopted methodologies, the paper will verify the contribution given by the INSURE methodology to research in the fields of modelling and indicators approaches, providing insights over methodological adjustments and the results obtained from the application to Lombardy. The conclusions will show how the methodology has tried to overcome identified constraints in current models, like the strong dependence on existing datasets of the obtained representations, the under-coverage of “immaterial factors” role and the scarce integration between sustainability dimensions.ustainable Development, Regional Economics, Econometric and Input Output Models, Development Planning and Policy, Regional Analyses

The Art of Fault Injection

Classical greek philosopher considered the foremost virtues to be temperance, justice, courage, and prudence. In this paper we relate these cardinal virtues to the correct methodological approaches that researchers should follow when setting up a fault injection experiment. With this work we try to understand where the "straightforward pathway" lies, in order to highlight those common methodological errors that deeply influence the coherency and the meaningfulness of fault injection experiments. Fault injection is like an art, where the success of the experiments depends on a very delicate balance between modeling, creativity, statistics, and patience

Development of a software safety process and a case study of its use

The goal of this research is to continue the development of a comprehensive approach to software safety and to evaluate the approach with a case study. The case study is a major part of the project, and it involves the analysis of a specific safety-critical system from the medical equipment domain. The particular application being used was selected because of the availability of a suitable candidate system. We consider the results to be generally applicable and in no way particularly limited by the domain. The research is concentrating on issues raised by the specification and verification phases of the software lifecycle since they are central to our previously-developed rigorous definitions of software safety. The theoretical research is based on our framework of definitions for software safety. In the area of specification, the main topics being investigated are the development of techniques for building system fault trees that correctly incorporate software issues and the development of rigorous techniques for the preparation of software safety specifications. The research results are documented. Another area of theoretical investigation is the development of verification methods tailored to the characteristics of safety requirements. Verification of the correct implementation of the safety specification is central to the goal of establishing safe software. The empirical component of this research is focusing on a case study in order to provide detailed characterizations of the issues as they appear in practice, and to provide a testbed for the evaluation of various existing and new theoretical results, tools, and techniques. The Magnetic Stereotaxis System is summarized

Reliability Analysis of Complex NASA Systems with Model-Based Engineering

The emergence of model-based engineering, with Model- Based Systems Engineering (MBSE) leading the way, is transforming design and analysis methodologies. The recognized benefits to systems development include moving from document-centric information systems and document-centric project communication to a model-centric environment in which control of design changes in the life cycles is facilitated. In addition, a single source of truth about the system, that is up-to-date in all respects of the design, becomes the authoritative source of data and information about the system. This promotes consistency and efficiency in regard to integration of the system elements as the design emerges and thereby may further optimize the design. Therefore Reliability Engineers (REs) supporting NASA missions must be integrated into model-based engineering to ensure the outputs of their analyses are relevant and value-needed to the design, development, and operational processes for failure risks assessment and communication