This paper presents and evaluates the Boundary Diagram Tool for change impact analysis of large Simulink designs of embedded systems. In our previous work, we developed the Reach/Coreach Tool for model slicing within a single Simulink model. The current work extends the Reach/Coreach Tool to trace the impact of model changes through multiple models comprising an embedded system, including network interfaces. The change impact analysis results are represented using various diagrams motivated by industrial needs. Several techniques are used to improve understanding of impact analyses of large industrial systems. The tool has been integrated into the software development process of a large automotive OEM (Original Equipment Manufacturer) to support the following activities: change request analysis and evaluation, implementation, verification and integration. The tool also aids impact analyses required for compliance with functional safety standards. The tool’s effectiveness has been demonstrated on production-scale models.

In the Matlab Simulink environment, systems can be modelled using Simulink block diagrams and Stateflow state charts. While stateful logic is more naturally modelled using Stateflow, in practice complex block diagrams are often used instead, resulting in models that are hard to understand and maintain. In order to improve the maintainability and understandability of large industrial models, this paper presents a strategy for refactoring Simulink block diagrams implementing stateful logic into functionally equivalent Stateflow state charts that more naturally represent the intended behaviour. To bridge the gap between the syntax of block diagrams and state charts, Mealy machines represented by tabular expressions are used as an intermediate representation. The compositional language of block diagrams is used to combine tables modelling individual blocks into a table for the entire block diagram which describes the high level state machine encoded in the Simulink subsystem. A prototype tool that performs the translation from Simulink to Stateflow automatically is discussed.

Assurance is a demonstration that a complex system (such as a car or a communication network) possesses an importantproperty, such as safety or security, with a high level of confidence. In contrast to currently dominant approaches to building assurance cases, which are focused on goal structuring and/or logical inference, we propose considering assurance as a model transformation (MT) enterprise: saying that a system possesses an assured property amounts to saying that a particular assurance view of the system comprising the assurance data, satisfies acceptance criteria posed as assurance constraints. While the MT realizing this view is very complex, we show that it can be decomposed into elementary MTs via a hierarchy of refinement steps. The transformations at the bottom level are ordinary MTs that can be executed for data specifying the system, thus providing the assurance data to be checked against the assurance constraints. In this way, assurance amounts to traversing the hierarchy from the top to the bottom and assuring the correctness of each MT in the path. Our approach has a precise mathematical foundation (rooted in process algebra and category theory) --- a necessity if we are to model precisely and then analyze our assurance cases. We discuss the practical applicability of the approach, and argue that it has several advantages over existing approaches.