Cost Automata, Safe Schemes, and Downward Closures
Abstract
In this work we prove decidability of the model-checking problem for safe recursion schemes against properties defined by alternating B-automata. We then exploit this result to show how to compute downward closures of languages of finite trees recognized by safe recursion schemes. Higher-order recursion schemes are an expressive formalism used to define languages of finite and infinite ranked trees by means of fixed points of lambda terms. They extend regular and context-free grammars, and are equivalent in expressive power to the simply typed -calculus and collapsible pushdown automata. Safety in a syntactic restriction which limits their expressive power. The class of alternating B-automata is an extension of alternating parity automata over infinite trees; it enhances them with counting features that can be used to describe boundedness properties.
Cite
@article{arxiv.2004.12187,
title = {Cost Automata, Safe Schemes, and Downward Closures},
author = {David Barozzini and Lorenzo Clemente and Thomas Colcombet and Paweł Parys},
journal= {arXiv preprint arXiv:2004.12187},
year = {2024}
}