A Methodology for the Simplification of Tabular Designs in Model-Based Development

Abstract

Model-based development (MBD) is an increasingly used approach for the development of embedded control software, with Matlab Simulink/Stateflow as the widely accepted language. The adoption of this development paradigm is prevalent in many safety-critical domains, including the automotive industry. With an increasing reliance on software for controlling vehicle functionality and the yearly advent of new vehicle features, automotive models have been growing in size and complexity, causing them to become increasingly difficult to maintain, refactor, and test. Given the centrality of models in MBD, it is a requisite that they be maintained under well-defined and principled software development processes that use precise notation to document system requirements and behavioural design description.Tabular methods have long been used for defining decision-making logic in software, due to their concise and precise manner of communicating complex behaviour, so it is not surprising that they are finding increased use in automotive software models. Thus their presence in Simulink models is increasingly prominent in the implementation of complex behaviour in production code. As a result of the safety-critical nature of the automotive industry, as well as the increasing size and complexity of its models, reliable refactoring and simplification techniques for tabular expressions are becoming an important need for automotive companies. To address this need, this thesis presents a methodology for refactoring complex tabular designs to improve requirements traceability with a focus on Matlab Simulink/Stateflow and the MBD approach.A case study of industrial examples from an automotive partner are used to motivate the work and demonstrate the proposed methodology's effectiveness in reducing design size and complexity, while also increasing testability and requirements traceability.iii

SL2SF: Refactoring Simulink to Stateflow

“…Tabular expressions were given a precise semantics in [10]. The structure of tables can be rearranged without changing the function they describe, e.g., conditions can be reordered as in [4]; conditions can be combined with subconditions (via conjunction) to flatten the hierarchy of conditions; and normal expressions in the table can be simplified by assuming the conditions to their left hold.…”