Faithful (meta-)encodings of programmable strategies into term rewriting systems

TL;DR

This paper presents a generic, sound, and complete encoding of programmable rewriting strategies into plain term rewriting systems, enabling the use of existing termination analysis tools for strategy-controlled rewriting.

Contribution

It introduces a novel encoding method for rewriting strategies into term rewriting systems, compatible with existing termination tools and adaptable to many-sorted signatures and meta-level representations.

Findings

Encoding is sound and complete for classic strategies

Termination analysis tools can be applied to encoded strategies

Implementation in Tom shows comparable performance to native strategies

Abstract

Rewriting is a formalism widely used in computer science and mathematical logic. When using rewriting as a programming or modeling paradigm, the rewrite rules describe the transformations one wants to operate and rewriting strategies are used to con- trol their application. The operational semantics of these strategies are generally accepted and approaches for analyzing the termination of specific strategies have been studied. We propose in this paper a generic encoding of classic control and traversal strategies used in rewrite based languages such as Maude, Stratego and Tom into a plain term rewriting system. The encoding is proven sound and complete and, as a direct consequence, estab- lished termination methods used for term rewriting systems can be applied to analyze the termination of strategy controlled term rewriting systems. We show that the encoding of strategies into term rewriting systems can be easily adapted to handle many-sorted signa- tures and we use a meta-level representation of terms to reduce the size of the encodings. The corresponding implementation in Tom generates term rewriting systems compatible with the syntax of termination tools such as AProVE and TTT2, tools which turned out to be very effective in (dis)proving the termination of the generated term rewriting systems. The approach can also be seen as a generic strategy compiler which can be integrated into languages providing pattern matching primitives; experiments in Tom show that applying our encoding leads to performances comparable to the native Tom strategies.