The Complexity of Codiagnosability for Discrete Event and Timed Systems

TL;DR

This paper investigates the computational complexity of fault codiagnosis in discrete event and timed automata, establishing PSPACE-completeness and 2EXPTIME-completeness results that improve and extend prior knowledge.

Contribution

It provides a unified characterization of codiagnosability for FA and TA, and determines the exact complexity classes for these problems, including a new result for timed automata.

Findings

Codiagnosability is PSPACE-complete for both FA and TA.

The problem is 2EXPTIME-complete for TA under bounded resources.

Improves the known complexity bound for FA from EXPTIME to PSPACE.

Abstract

In this paper we study the fault codiagnosis problem for discrete event systems given by finite automata (FA) and timed systems given by timed automata (TA). We provide a uniform characterization of codiagnosability for FA and TA which extends the necessary and sufficient condition that characterizes diagnosability. We also settle the complexity of the codiagnosability problems both for FA and TA and show that codiagnosability is PSPACE-complete in both cases. For FA this improves on the previously known bound (EXPTIME) and for TA it is a new result. Finally we address the codiagnosis problem for TA under bounded resources and show it is 2EXPTIME-complete.