Type Inference of Simulink Hierarchical Block Diagrams in Isabelle

TL;DR

This paper introduces a method for inferring types in hierarchical Simulink block diagrams using Isabelle, enabling formal analysis of complex models with potential ambiguities, demonstrated on real-world case studies.

Contribution

It presents a novel approach to type inference for Simulink diagrams within Isabelle, extending previous frameworks to include formal type checking capabilities.

Findings

Successfully inferred types for complex diagrams

Handled diagrams with typing ambiguities

Validated on automotive case studies

Abstract

Simulink is a de-facto industrial standard for the design of embedded systems. In previous work, we developed a compositional analysis framework for Simulink models in Isabelle -- the Refinement Calculus of Reactive Systems (RCRS), which allows checking compatibility and substitutability of components. However, standard type checking was not considered in that work. In this paper we present a method for the type inference of hierarchical block diagrams using the Isabelle theorem prover. A Simulink diagram is translated into an (RCRS) Isabelle theory. Then the Isabelle's powerful type inference mechanism is used to infer the types of the diagram based on the types of the basic blocks. One of the aims is to handle formally as many diagrams as possible. In particular, we want to be able to handle even those diagrams that may have typing ambiguities, provided that they are accepted by Simulink. This method is implemented in our toolset that translates Simulink diagrams into Isabelle theories and simplifies them. We evaluate our technique on several case studies, most notably, an automotive fuel control system benchmark provided by Toyota.