Seong-heum Kim
Author directoryAlso published as: Seong-Heum Kim
2026
FACET at WMT 2026 Automated Translation Quality Evaluation Task
Ahrii Kim | Chanjun Park | Seong-Heum Kim
Proceedings of the Eleventh Conference on Machine Translation
Ahrii Kim | Chanjun Park | Seong-Heum Kim
Proceedings of the Eleventh Conference on Machine Translation
Different error types in machine translation require different evidence. Whether meaning is preserved can be judged only against the source, while whether the target is well-formed, or whether it names one entity consistently, can be judged from the target alone. We present FACET, our reference-free submission to the WMT26 Automated Translation Quality Evaluation Task, which decomposes evaluation into Fluency, Accuracy, and Consistency passes and gives each pass only the context its error type requires. A single fixed model is prompted three times, and the merged error spans yield the three task outputs, error spans, quality scores, and error-free labels, with no trained components. We also submit FACET−C, which omits the Consistency pass. Without gold labels, we characterize the predictions of FACET. Its system rankings place post-edited human translation first, and the Consistency pass changes about a tenth of segment scores while leaving the ranking nearly unchanged.
The Blindness of Document-Level Translation Evaluation
Ahrii Kim | Vilém Zouhar | Chanjun Park | Seong-heum Kim
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Ahrii Kim | Vilém Zouhar | Chanjun Park | Seong-heum Kim
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Document-level machine translation (MT) evaluation extends segment-level protocols by presenting full documents to annotators, on the assumption that such presentation elicits document-level judgments. We test this assumption with a counterfactual condition (MIX) in which each document combines segments drawn from different systems, preserving document-level presentation while breaking cross-segment consistency. Across 18,420 expert English→Korean annotations and 14 automatic metrics, scores, system rankings, and error annotations are statistically equivalent between coherent and incoherent documents. Perception does not explain this: shown matched passages, raters identify the coherent one as the work of a single translator in 87.3% of trials. Document presentation does change how annotators work, but that change does not reach the recorded output. What is blind is the protocol, not the annotator. The concern is not that scores fall short, but that the resources invested in document-level systems, metrics, and annotation may not be measuring what they are intended to measure.
Discourse Dependency: A Continuous Criterion for Translation Difficulty
Ahrii Kim | Chanjun Park | Seong-heum Kim
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Ahrii Kim | Chanjun Park | Seong-heum Kim
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Recent calls for harder machine translation benchmarks have not clarified what difficulty should mean. We argue that one meaningful and currently unmeasured axis is referential reach, the distance a segment must look back into its document to resolve the entities and pronouns it contains. We formalize this as discourse dependency (DDP), a metric-free, source-side measure computed from named entity re-mentions and pronominal coreference. Validated against gold coreference, DDP errs one-sidedly in 99.2% of segments, so a high-DDP segment is certified to require long-range context. Applying DDP to WMT24++ and WMT25 shows that both are heavily skewed toward low-DDP segments, which domain labels do not distinguish. Building on DDP, we compare five context injection strategies in an English-Korean post-editing setup, varying context size and selection. As DDP grows, no strategy keeps pace with human post-editing. On segments with DDP ≥ 15 raters prefer human translations, while automatic metrics register no difference. As frontier systems saturate aggregate scores, DDP shifts evaluation from how well models score to how far they can reach.