NaDeA: A Natural Deduction Assistant with a Formalization in Isabelle

TL;DR

NaDeA is an open-source, browser-based natural deduction teaching tool, formally verified in Isabelle, designed for undergraduates but applicable to broader audiences and other proof systems.

Contribution

It introduces a formally verified natural deduction proof system in Isabelle, implemented as an accessible web tool for educational purposes.

Findings

Proof system formalized and proved sound in Isabelle

Browser-based tool accessible without installation

Designed for undergraduate computer science education

Abstract

We present a new software tool for teaching logic based on natural deduction. Its proof system is formalized in the proof assistant Isabelle such that its definition is very precise. Soundness of the formalization has been proved in Isabelle. The tool is open source software developed in TypeScript / JavaScript and can thus be used directly in a browser without any further installation. Although developed for undergraduate computer science students who are used to study and program concrete computer code in a programming language we consider the approach relevant for a broader audience and for other proof systems as well.