CTL* synthesis via LTL synthesis

TL;DR

This paper presents a method to reduce CTL* synthesis to LTL synthesis by encoding witnesses of CTL* subformulas into system outputs, enabling the use of LTL synthesis techniques for CTL* properties.

Contribution

It introduces a novel reduction from CTL* synthesis to LTL synthesis that preserves complexity and allows leveraging existing LTL synthesis tools.

Findings

Reduction preserves problem complexity

Implemented and evaluated on multiple examples

Potential increase in minimal system size

Abstract

We reduce synthesis for CTL* properties to synthesis for LTL. In the context of model checking this is impossible - CTL* is more expressive than LTL. Yet, in synthesis we have knowledge of the system structure and we can add new outputs. These outputs can be used to encode witnesses of the satisfaction of CTL* subformulas directly into the system. This way, we construct an LTL formula, over old and new outputs and original inputs, which is realisable if, and only if, the original CTL* formula is realisable. The CTL*-via-LTL synthesis approach preserves the problem complexity, although it might increase the minimal system size. We implemented the reduction, and evaluated the CTL*-via-LTL synthesiser on several examples.