@inproceedings{lee-etal-2026-hico,
title = "{H}i{C}o-{EL}: Encoding Ontology Structure into Bi-Encoder Entity Linking",
author = "Lee, Albert and
Bathala, Prasanth and
Malhotra, Puru and
Ye, Christophe and
Mitchell, Cassie S.",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.103/",
pages = "2113--2123",
ISBN = "979-8-89176-462-0",
abstract = "Bi-encoder architectures for biomedical entity linking learn flat embedding spaces that ignore ontology structure. HiCo-EL encodes hierarchical knowledge into bi-encoder representations through hierarchical contrastive pretraining. The core idea is within-space hierarchical multi-label contrastive learning (HMLC): contrastive losses applied independently within each encoder space, preserving cross-space compatibility for retrieval. Our formulation drops the monotonicity constraints of prior HMLC work, handles variable-depth hierarchy paths, and adds depth-weighted alignment between encoder spaces. Treating each entity as a leaf node unifies coarse type structure with fine-grained entity discrimination. On MedMentions and NCBI Disease, HiCo-EL outperforms ArboEL by +3.7{\%} and +1.8{\%} Recall@1 respectively. The gains reveal a key insight: breadth amplifies, depth generalizes{---}broad hierarchies help common entities most (+6.3{\%} R@1), while deep hierarchies benefit unseen entities (+9.6{\%} R@1 zero-shot)."
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<abstract>Bi-encoder architectures for biomedical entity linking learn flat embedding spaces that ignore ontology structure. HiCo-EL encodes hierarchical knowledge into bi-encoder representations through hierarchical contrastive pretraining. The core idea is within-space hierarchical multi-label contrastive learning (HMLC): contrastive losses applied independently within each encoder space, preserving cross-space compatibility for retrieval. Our formulation drops the monotonicity constraints of prior HMLC work, handles variable-depth hierarchy paths, and adds depth-weighted alignment between encoder spaces. Treating each entity as a leaf node unifies coarse type structure with fine-grained entity discrimination. On MedMentions and NCBI Disease, HiCo-EL outperforms ArboEL by +3.7% and +1.8% Recall@1 respectively. The gains reveal a key insight: breadth amplifies, depth generalizes—broad hierarchies help common entities most (+6.3% R@1), while deep hierarchies benefit unseen entities (+9.6% R@1 zero-shot).</abstract>
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%0 Conference Proceedings
%T HiCo-EL: Encoding Ontology Structure into Bi-Encoder Entity Linking
%A Lee, Albert
%A Bathala, Prasanth
%A Malhotra, Puru
%A Ye, Christophe
%A Mitchell, Cassie S.
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F lee-etal-2026-hico
%X Bi-encoder architectures for biomedical entity linking learn flat embedding spaces that ignore ontology structure. HiCo-EL encodes hierarchical knowledge into bi-encoder representations through hierarchical contrastive pretraining. The core idea is within-space hierarchical multi-label contrastive learning (HMLC): contrastive losses applied independently within each encoder space, preserving cross-space compatibility for retrieval. Our formulation drops the monotonicity constraints of prior HMLC work, handles variable-depth hierarchy paths, and adds depth-weighted alignment between encoder spaces. Treating each entity as a leaf node unifies coarse type structure with fine-grained entity discrimination. On MedMentions and NCBI Disease, HiCo-EL outperforms ArboEL by +3.7% and +1.8% Recall@1 respectively. The gains reveal a key insight: breadth amplifies, depth generalizes—broad hierarchies help common entities most (+6.3% R@1), while deep hierarchies benefit unseen entities (+9.6% R@1 zero-shot).
%U https://aclanthology.org/2026.findings-emnlp.103/
%P 2113-2123
Markdown (Informal)
[HiCo-EL: Encoding Ontology Structure into Bi-Encoder Entity Linking](https://aclanthology.org/2026.findings-emnlp.103/) (Lee et al., Findings 2026)
ACL