Conformance Testing as Falsification for Cyber-Physical Systems

TL;DR

This paper introduces a universal, distance-based notion of conformance for cyber-physical systems, providing algorithms to detect non-conformance and measure how closely systems match, applicable to models and implementations.

Contribution

It defines a rigorous, universal conformance measure as system closeness and develops algorithms for non-conformance detection and degree measurement for industrial systems.

Findings

Proposed a universal conformance measure based on system distance

Developed an algorithm to detect non-conformance using existing tools

Demonstrated methods on various models

Abstract

In Model-Based Design of Cyber-Physical Systems (CPS), it is often desirable to develop several models of varying fidelity. Models of different fidelity levels can enable mathematical analysis of the model, control synthesis, faster simulation etc. Furthermore, when (automatically or manually) transitioning from a model to its implementation on an actual computational platform, then again two different versions of the same system are being developed. In all previous cases, it is necessary to define a rigorous notion of conformance between different models and between models and their implementations. This paper argues that conformance should be a measure of distance between systems. Albeit a range of theoretical distance notions exists, a way to compute such distances for industrial size systems and models has not been proposed yet. This paper addresses exactly this problem. A universal notion of conformance as closeness between systems is rigorously defined, and evidence is presented that this implies a number of other application-dependent conformance notions. An algorithm for detecting that two systems are not conformant is then proposed, which uses existing proven tools. A method is also proposed to measure the degree of conformance between two systems. The results are demonstrated on a range of models.