Span-Level Machine Translation Meta-Evaluation

Stefano Perrella, Eric Morales Agostinho, Hugo Zaragoza


Abstract
Machine Translation (MT) and automatic MT evaluation have improved dramatically in recent years, enabling numerous novel applications. Automatic evaluation techniques have evolved from producing scalar quality scores to precisely locating translation errors and assigning them error categories and severity levels. However, it remains unclear how to reliably measure the evaluation capabilities of auto-evaluators that do error detection, as no established technique exists in the literature. This work investigates different implementations of span-level precision, recall, and *F*-score, showing that seemingly similar approaches can yield substantially different rankings, and that certain widely-used techniques are unsuitable for evaluating MT error detection. We propose "match with partial overlap and partial credit" (MPP) with micro-averaging as a robust meta-evaluation strategy and release code for its use publicly. Finally, we use MPP to assess the state of the art in MT error detection.
Anthology ID:
2026.emnlp-main.2213
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
50342–50361
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2213/
DOI:
Bibkey:
Cite (ACL):
Stefano Perrella, Eric Morales Agostinho, and Hugo Zaragoza. 2026. Span-Level Machine Translation Meta-Evaluation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 50342–50361, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Span-Level Machine Translation Meta-Evaluation (Perrella et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.2213.pdf