On the Hardness of Learning Regular Expressions

Fuente: arXiv
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Autores principales: Attias, Idan, Reyzin, Lev, Srebro, Nathan, Vardi, Gal
Formato: Preprint
Publicado: 2025
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author Attias, Idan
Reyzin, Lev
Srebro, Nathan
Vardi, Gal
author_facet Attias, Idan
Reyzin, Lev
Srebro, Nathan
Vardi, Gal
contents Despite the theoretical significance and wide practical use of regular expressions, the computational complexity of learning them has been largely unexplored. We study the computational hardness of improperly learning regular expressions in the PAC model and with membership queries. We show that PAC learning is hard even under the uniform distribution on the hypercube, and also prove hardness of distribution-free learning with membership queries. Furthermore, if regular expressions are extended with complement or intersection, we establish hardness of learning with membership queries even under the uniform distribution. We emphasize that these results do not follow from existing hardness results for learning DFAs or NFAs, since the descriptive complexity of regular languages can differ exponentially between DFAs, NFAs, and regular expressions.
format Preprint
id arxiv_https___arxiv_org_abs_2510_04834
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle On the Hardness of Learning Regular Expressions
Attias, Idan
Reyzin, Lev
Srebro, Nathan
Vardi, Gal
Machine Learning
Computational Complexity
Despite the theoretical significance and wide practical use of regular expressions, the computational complexity of learning them has been largely unexplored. We study the computational hardness of improperly learning regular expressions in the PAC model and with membership queries. We show that PAC learning is hard even under the uniform distribution on the hypercube, and also prove hardness of distribution-free learning with membership queries. Furthermore, if regular expressions are extended with complement or intersection, we establish hardness of learning with membership queries even under the uniform distribution. We emphasize that these results do not follow from existing hardness results for learning DFAs or NFAs, since the descriptive complexity of regular languages can differ exponentially between DFAs, NFAs, and regular expressions.
title On the Hardness of Learning Regular Expressions
topic Machine Learning
Computational Complexity
url https://arxiv.org/abs/2510.04834