Structured Document Translation via Format Reinforcement Learning
Authors: name: Haiyue Song, name: Johannes Eschbach-Dymanus, name: Hour Kaing, name: Sumire Honda, name: Hideki Tanaka, name: Bianka Buschbeck, name: Masao Utiyama
Organization: Advanced Translation Technology Lab at ASTREC, NICT

Recent works on structured text translation remain limited to the sentence level, as they struggle to effectively handle the complex document-level XML or HTML structures. To address this, we propose Format Reinforcement Learning (FormatRL), which employs Group Relative Policy Optimization on top of a supervised fine-tuning model to directly optimize novel structure-aware rewards: 1) TreeSim, which measures structural similarity between predicted and reference XML trees and 2) Node-chrF, which measures translation quality at the level of XML nodes. Additionally, we apply StrucAUC, a fine-grained metric distinguishing between minor errors and major structural failures. Experiments on the SAP software-documentation benchmark demonstrate improvements across six metrics and an analysis further shows how different reward functions contribute to improvements in both structural and translation quality.