CTL* Verification and Synthesis using Existential Horn Clauses

TL;DR

This paper introduces a new method for verifying and synthesizing infinite-state reactive programs against CTL* specifications by translating the problem into Existential Horn Clauses and solving them.

Contribution

It presents a translation system and algorithms for CTL* verification and synthesis using EHCs, extending previous Horn clause techniques with existential quantification.

Findings

The translation system extit{Trans} effectively converts verification problems into satisfiable EHCs.

The algorithms are proven sound and relatively complete for CTL* verification and synthesis.

Case studies demonstrate the practical applicability of the approach.

Abstract

This work proposes a novel approach for automatic verification and synthesis of infinite-state reactive programs with respect to ${CTL}^*$ specifications, based on translation to Existential Horn Clauses (EHCs). $CTL^*$ is a powerful temporal logic, which subsumes the temporal logics LTL and CTL, both widely used in specification, verification, and synthesis of complex systems. EHCs with its solver E-HSF, is an extension of Constrained Horn Clauses, which includes existential quantification as well as the power of handling well-foundedness. We develop the translation system \textit{Trans}, which given a verification problem consisting of a program $P$ and a specification $\phi$, builds a set of EHCs which is satisfiable iff $P$ satisfies $\phi$. We also develop a synthesis algorithm that given a program with holes in conditions and assignments, fills the holes so that the synthesized program satisfies the given $CTL^*$ specification. We prove that our verification and synthesis algorithms are both sound and relative complete. Finally, we present case studies to demonstrate the applicability of our algorithms for $CTL^*$ verification and synthesis.