STAR : Sentence Translation Alignment Rate for Document-to-Document Machine Translation

Yichen Dong, Hao Wang, Junhui Li, Linlong Xu, Longyue Wang, Weihua Luo


Abstract
Large Language Models (LLMs) have enabled a shift from sentence-level to document-to-document (Doc2Doc) machine translation, promising improved global coherence. However, document-to-document generation in a single pass frequently suffers from structural misalignment, manifesting as sentence omissions or hallucinations that violate the core requirement of source-target correspondence. To address this, we introduce **S**entence **T**ranslation **A**lignment **R**ate (**STAR**), an auxiliary metric that explicitly quantifies sentence-level structural fidelity. Building on this, we propose **STAR**-masked **P**reference **O**ptimization (**StarPO**), a framework that ranks document-level hypotheses by structural quality and utilizes a dynamic alignment mask to focus optimization on misaligned segments. Experimental results across news and literary domains demonstrate that StarPO significantly enhances translation quality and structural integrity. Notably, StarPO allows compact models to surpass the performance of massive proprietary systems like GPT-4o while maintaining superior token efficiency. We will release our code and datasets.
Anthology ID:
2026.findings-emnlp.699
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
14667–14689
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.699/
DOI:
10.18653/2026.findings-emnlp.699
Bibkey:
Cite (ACL):
Yichen Dong, Hao Wang, Junhui Li, Linlong Xu, Longyue Wang, and Weihua Luo. 2026. STAR : Sentence Translation Alignment Rate for Document-to-Document Machine Translation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 14667–14689, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
STAR : Sentence Translation Alignment Rate for Document-to-Document Machine Translation (Dong et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.699.pdf