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Chinese Spelling Correction as Rephrasing Language Model
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Proposes ReLM, which fine-tunes BERT to rephrase the whole sentence into mask slots instead of character-level tagging for Chinese spelling correction, achieving SOTA on ECSpell and LEMON and better multi-task transfer.
Problem
Chinese spelling correction models trained as character-to-character sequence tagging over-condition corrections on memorized error patterns, which hurts generalization, zero-shot transfer, and multi-task learning.
Approach
Replace character-level tagging with a rephrasing objective: concatenate the source sentence with a same-length sequence of mask characters and train a BERT-style masked LM to infill the whole corrected sentence, plus auxiliary masking of non-error characters to discourage learning alignment shortcuts.
Key results
- ReLM reaches F1 91.2, 82.4, and 83.6 on ECSpell LAW, MED, and ODW, beating the previous masked-fine-tuned SOTA by 10.6, 12.8, and 16.7 points.
- On zero-shot LEMON, ReLM raises the average F1 from 49.7 to 51.2 over prior tagging SOTA.
- In multi-task training, ReLM (prompt) keeps CSC F1 at 87.6 on LAW versus 62.0 for BERT-MFT tagging, and it lowers false positive rate to 6.8% average versus 13.8%.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Replace character tagging with full-sentence rephrasing using fixed-length mask infilling | BERT on CSC · ECSpell LAW, MED, and ODW | F1: 80.6 -> 91.2; 69.6 -> 82.4; 66.9 -> 83.6 | Helped |
| Replace tagging with full-sentence rephrasing | BERT on zero-shot CSC · LEMON average | F1: 49.7 -> 51.2 | Helped |
| Replace tagging with full-sentence rephrasing | BERT on zero-shot CSC · LEMON GAM and NOV | F1: 33.3 -> 33.0; 38.6 -> 37.8 | Mixed |
| Apply rephrasing rather than tagging | GPT2 on CSC · ECSpell LAW | F1: 39.8 -> 71.2 | Helped |
| Mask only non-error characters rather than any characters for auxiliary MLM (ablation) | ReLM · ECSpell average | F1: 85.8 -> 88.1 | Helped |
| Set auxiliary MLM mask rate to 0% (ablation) | ReLM · ECSpell average | F1: 28.4 -> 57.8 | Hurt |
| Increase auxiliary MLM mask rate from 10% to 20% (ablation) | ReLM · ECSpell average | F1: 85.6 -> 87.7 | Helped |
| Increase auxiliary MLM mask rate from 20% to 30% (ablation) | ReLM · ECSpell average | F1: 87.7 -> 88.1 | Helped |
| Increase auxiliary MLM mask rate from 30% to 40% (ablation) | ReLM · ECSpell average | F1: 88.1 -> 86.3 | Hurt |
| Increase auxiliary MLM mask rate from 40% to 60% (ablation) | ReLM · ECSpell average | F1: 86.3 -> 82.4 | Hurt |
| Add learnable task prompts (ablation) | ReLM in multi-task CSC · ECSpell LAW, MED, and ODW | F1: 84.2 -> 87.6; 76.1 -> 80.8; 75.0 -> 78.0 | Helped |
| Jointly train CSC with other tasks | BERT tagging · ECSpell LAW, MED, and ODW | F1: 34.5; 15.1; 16.8 | Hurt |
Surprising findings
- ChatGPT with 10-shot prompting performs poorly on CSC (e.g., F1 26.0 on MED), which the authors attribute to lack of high-quality annotated CSC data on the web.
- Even a GPT2 model trained with the rephrasing objective outperforms BERT tagging by a large margin (F1 71.2 vs 39.8 on LAW).
Limitations
- Zero-shot LEMON training relies on 34 million synthesized sentence pairs, so gains depend on large synthetic data.
- Auto-regressive rephrasing (GPT2) underperforms ReLM, and the paper gives no in-depth study of why beyond fixed-length matching.
- Mask rate and strategy were tuned on the evaluation domains, with the authors noting results still depend on specific data.
Experimental setup
Datasets: ECSpell LEMON SIGHAN AFQMC TNEWS
Benchmarks: ECSpell LEMON SIGHAN AFQMC TNEWS
Metrics: precision recall F1 false positive rate
Baselines: BERT-Tagging BERT-MFT MDCSpell-MFT Soft-Masked-MFT CRASpell-MFT GPT2-Tagging Baichuan2-7B ChatGPT
Builds on: BERT masked fine-tuning MDCSpell prompt tuning
Closest papers by meaning
- CEC-Zero: Zero-Supervision Character Error Correction with Self-Generated Rewards (AAAI 2026 · similarity 0.89)
- ScholarGEC: Enhancing Controllability of Large Language Model for Chinese Academic Grammatical Error Correction (AAAI 2025 · similarity 0.86)
- Learning from Mistakes: Self-correct Adversarial Training for Chinese Unnatural Text Correction (AAAI 2025 · similarity 0.86)
- EXCGEC: A Benchmark for Edit-Wise Explainable Chinese Grammatical Error Correction (AAAI 2025 · similarity 0.82)
- RewriteLM: An Instruction-Tuned Large Language Model for Text Rewriting (AAAI 2024 · similarity 0.81)
- Learning from others' mistakes: Finetuning machine translation models with span-level error annotations (ICML 2025 · similarity 0.80)
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