Hierarchical Bracketing Encodings for Dependency Parsing as Tagging

Fuente: arXiv
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Main Authors: Ezquerro, Ana, Vilares, David, Yli-Jyrä, Anssi, Gómez-Rodríguez, Carlos
Format: Preprint
Published: 2025
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author Ezquerro, Ana
Vilares, David
Yli-Jyrä, Anssi
Gómez-Rodríguez, Carlos
author_facet Ezquerro, Ana
Vilares, David
Yli-Jyrä, Anssi
Gómez-Rodríguez, Carlos
contents We present a family of encodings for sequence labeling dependency parsing, based on the concept of hierarchical bracketing. We prove that the existing 4-bit projective encoding belongs to this family, but it is suboptimal in the number of labels used to encode a tree. We derive an optimal hierarchical bracketing, which minimizes the number of symbols used and encodes projective trees using only 12 distinct labels (vs. 16 for the 4-bit encoding). We also extend optimal hierarchical bracketing to support arbitrary non-projectivity in a more compact way than previous encodings. Our new encodings yield competitive accuracy on a diverse set of treebanks.
format Preprint
id arxiv_https___arxiv_org_abs_2505_11693
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hierarchical Bracketing Encodings for Dependency Parsing as Tagging
Ezquerro, Ana
Vilares, David
Yli-Jyrä, Anssi
Gómez-Rodríguez, Carlos
Computation and Language
We present a family of encodings for sequence labeling dependency parsing, based on the concept of hierarchical bracketing. We prove that the existing 4-bit projective encoding belongs to this family, but it is suboptimal in the number of labels used to encode a tree. We derive an optimal hierarchical bracketing, which minimizes the number of symbols used and encodes projective trees using only 12 distinct labels (vs. 16 for the 4-bit encoding). We also extend optimal hierarchical bracketing to support arbitrary non-projectivity in a more compact way than previous encodings. Our new encodings yield competitive accuracy on a diverse set of treebanks.
title Hierarchical Bracketing Encodings for Dependency Parsing as Tagging
topic Computation and Language
url https://arxiv.org/abs/2505.11693