Signal-Based Properties of Cyber-Physical Systems: Taxonomy and Logic-based Characterization

TL;DR

This paper introduces a taxonomy of signal-based properties in cyber-physical systems, formalizes them in temporal logic, and evaluates their expressiveness and applicability through an industrial case study.

Contribution

It provides a comprehensive taxonomy and formalization of signal-based properties, aiding engineers in selecting appropriate specification languages for CPS requirements.

Findings

Taxonomy covers various signal property types with formal definitions.

Assesses the expressiveness of current temporal logics for these property types.

Demonstrates the taxonomy's applicability in an aerospace industrial case study.

Abstract

The behavior of a cyber-physical system (CPS) is usually defined in terms of the input and output signals processed by sensors and actuators. Requirements specifications of CPSs are typically expressed using signal-based temporal properties. Expressing such requirements is challenging, because of (1) the many features that can be used to characterize a signal behavior; (2) the broad variation in expressiveness of the specification languages (i.e., temporal logics) used for defining signal-based temporal properties. Thus, system and software engineers need effective guidance on selecting appropriate signal behavior types and an adequate specification language, based on the type of requirements they have to define. In this paper, we present a taxonomy of the various types of signal-based properties and provide, for each type, a comprehensive and detailed description as well as a formalization in a temporal logic. Furthermore, we review the expressiveness of state-of-the-art signal-based temporal logics in terms of the property types identified in the taxonomy. Moreover, we report on the application of our taxonomy to classify the requirements specifications of an industrial case study in the aerospace domain, in order to assess the feasibility of using the property types included in our taxonomy and the completeness of the latter.