SCRIPT: A Subcharacter Compositional Representation Injection Module for Korean Pre-Trained Language Models
Organizations: Department of Artificial Intelligence, Korea University, Seoul, South Korea · Department of Computer Science and Engineering, Korea University, Seoul, South Korea
Abstract
Korean is a morphologically rich language with a featural writing system in which each character is systematically composed of subcharacter units known as Jamo. These subcharacters not only determine the visual structure of Korean but also encode frequent and linguistically meaningful morphophonological processes. However, most current Korean language models (LMs) are based on subword tokenization schemes, which are not explicitly designed to capture the internal compositional structure of characters. To address this limitation, we propose SCRIPT, a model-agnostic module that injects subcharacter compositional knowledge into Korean PLMs. SCRIPT allows to enhance subword embeddings with structural granularity, without requiring architectural changes or additional pre-training. As a result, SCRIPT enhances all baselines across various Korean natural language understanding (NLU) and generation (NLG) tasks. Moreover, beyond performance gains, detailed linguistic analyses show that SCRIPT reshapes the embedding space in a way that better captures grammatical regularities and semantically cohesive variations. Our code is available at https://github.com/SungHo3268/SCRIPT.
Figures & tables
| Model | KorNLI | KorSTS | NSMC | PAWS-X | KoBEST | ||||
| BoolQ | COPA | WiC | HellaSwag | SentiNeg | |||||
| KOMBO | 75.97 | 77.28 | 88.34 | 73.40 | 61.40 | 61.00 | 68.91 | 63.80 | 79.07 |
| BERT | 75.85 | 76.72 | 88.96 | 72.38 | 60.75 | 60.90 | 73.14 | 63.20 | 83.12 |
| BERT + SCRIPT | 76.49 | 77.68 | 88.96 | 73.68 | 62.32 | 61.30 | 74.30 | 64.40 | 83.38 |
| KoGPT2 | 72.24 | 73.82 | 88.90 | 76.33 | 67.22 | 68.90 | 67.07 | 69.10 | 88.50 |
| KoGPT2 + SCRIPT | 72.47 | 74.27 | 88.80 | 76.61 | 68.28 | 70.90 | 68.18 | 72.40 | 89.47 |
| Model | KoCommonGen | ||||||
| BLEU 3 | BLEU 4 | ROUGE-2 | ROUGE-L | METEOR | mBERTScore | KoBERTScore | |
| KoGPT2 | 18.29 | 10.33 | 44.24 | 54.50 | 40.05 | 83.37 | 91.21 |
| KoGPT2 + SCRIPT | 25.01 | 15.57 | 47.42 | 60.00 | 42.53 | 84.67 | 91.46 |
| KoGPT3-1.2B | 26.19 | 17.20 | 58.85 | 62.53 | 52.11 | 85.41 | 91.17 |
| KoGPT3-1.2B + SCRIPT | 28.89 | 19.58 | 59.28 | 64.80 | 52.37 | 86.26 | 91.78 |
| EXAONE-2.4B | 40.11 | 28.41 | 62.25 | 64.84 | 54.84 | 87.65 | 93.12 |
| SCRIPT | Fusion w/ PLM | KoBEST | Avg. | |||||
| Initial Token Unit | Compression | BoolQ | COPA | WiC | HellaSwag | SentiNeg | ||
| Jamo | Principles | CrossAttention | 68.28 | 70.90 | 68.18 | 72.40 | 89.47 | 73.85 |
| Stroke | Principles | CrossAttention | 68.35 | 65.20 | 67.81 | 71.00 | 89.46 | 72.36 |
| Cji | Principles | CrossAttention | 68.82 | 65.20 | 67.98 | 71.40 | 88.01 | 72.28 |
| BTS | Principles | CrossAttention | 67.99 | 64.70 | 66.67 | 71.50 | 88.97 | 71.97 |
| Character | Principles | CrossAttention | 66.00 | 59.30 | 63.37 | 69.40 | 88.40 | 69.29 |
| Model | PLM Tokenization | KoBEST | Avg. | ||||
| BoolQ | COPA | WiC | HellaSwag | SentiNeg | |||
| BERT | Word | 60.04 | 5 7.60 | 62.70 | 55.00 | 5 2.39 | 57.55 |
| BERT + SCRIPT | 6 0.47 | 5 7.60 | 6 4.76 | 5 7.20 | 5 2.39 | 5 8.48( ▲ 0.94) | |
| BERT | Morpheme | 63.75 | 58.50 | 71.75 | 61.80 | 78.59 | 66.88 |
| BERT + SCRIPT | 6 5.03 | 6 0.00 | 72.06 | 6 2.20 | 8 0.35 | 6 7.93( ▲ 1.05) | |
| BERT | Subword | 67.22 | 67.10 | 68.90 | 69.10 | 88.50 | 72.16 |
Appendix figures & tables14 assets
Supplementary material from the paper’s appendix.
Appendix
| Input Character | Oracle Actions | Output Lemma Units |
| 런 (reon) | B-MOD-럽, I-MOD-ㄴ | 럽 (reob), ㄴ (n) |
| 했 (haess) | B-MOD-하, I-MOD-았 | 하 (ha), 았 (ass) |
| 다 (da) | B-KEEP | 다 (da) |
| Algorithm 1: Subword Representation with SCRIPT |
| Input: (raw input sentence), embedding dimension . |
| Output: (fused subword-level embeddings). |
| 1 // subcharacter sequence |
| 2 // subcharacter representation |
| 3 if first token in is [CLS] then // (for encoder-only model) |
| Task | Epoch | Batch Size | Learning Rate | Dropout Ratio | Warmup Ratio | LoRA r | LoRA |
| KorNLI | 5 | 64 | BERT: {5e-05, 1e-04} GPT : {1e-05, 5e-05, 1e-04, 1e-03, 3e-03, 1e-02} | 0.03 | 0.1 | 32 | 128 |
| KorSTS | 15 | 64 | |||||
| NSMC | 5 | 64 | |||||
| PAWS-X | 10 | 64 | |||||
| BoolQ | 10 | 8 | BERT: {1e-05, 5e-05} GPT : {1e-05, 5e-05, 1e-04, 1e-03, 3e-03, 1e-02} | 0.03 | 0.1 | 32 | 128 |
| COPA | 15 | 16 |
| Model | XL-Sum | ||||||
| BLEU 3 | BLEU 4 | ROUGE-2 | ROUGE-L | METEOR | mBERTScore | KoBERTScore | |
| KoGPT2 | 7.27 | 4.98 | 12.91 | 26.83 | 13.43 | 76.22 | 88.97 |
| KoGPT2 + SCRIPT | 7.64 | 5.20 | 13.30 | 27.24 | 13.67 | 76.31 | 89.20 |
| KoGPT3-1.2B | 9.14 | 6.21 | 15.88 | 30.18 | 16.91 | 76.95 | 89.69 |
| KoGPT3-1.2B + SCRIPT | 9.39 | 6.40 | 15.99 | 30.31 | 16.97 | 77.46 | 89.77 |
| Model | Kor-Learner | Kor-Native | ||||||
| GLEU | GLEU | |||||||
| KoGPT2 | 29.35 | 16.11 | 25.19 | 21.60 | 72.12 | 55.19 | 67.76 | 61.45 |
| KoGPT2 + SCRIPT | 30.02 | 16.83 | 25.34 | 23.54 | 72.95 | 56.15 | 69.00 | 62.25 |
| KoGPT3-1.2B | 47.05 | 23.01 | 38.89 | 35.22 | 84.76 | 69.54 | 81.20 | 75.21 |
| KoGPT3-1.2B + SCRIPT | 49.45 | 26.36 | 41.68 | 39.45 | 85.49 | 70.02 | 81.87 | 75.40 |
| Model | KoBEST | Avg. | ||||
| BoolQ | COPA | WiC | HellaSwag | SentiNeg | ||
| KoGPT3-1.2B | 77.32 | 82.80 | 72.78 | 78.90 | 96.31 | 81.62 |
| KoGPT3-1.2B + SCRIPT | 77.63 | 82.80 | 74.65 | 79.30 | 96.48 | 82.17 |
| mGPT-1.3B | 71.19 | 69.70 | 68.38 | 76.10 | 89.40 | 74.95 |
| mGPT-1.3B + SCRIPT | 70.72 | 70.60 | 69.17 | 76.70 | 90.42 | 75.52 |
| Model | KoCommonGen | Avg. | ||||||
| BLEU 3 | BLEU 4 | ROUGE-2 | ROUGE-L | METEOR | mBERTScore | KoBERTScore | ||
| KoGPT3-1.2B | 26.19 | 17.20 | 58.85 | 62.53 | 52.11 | 85.41 | 91.17 | 56.21 |
| KoGPT3-1.2B + SCRIPT | 28.89 | 19.58 | 59.28 | 64.80 | 52.37 | 86.26 | 91.78 | 57.57 |
| mGPT-1.3B | 15.16 | 8.07 | 37.77 | 50.99 | 33.31 | 80.17 | 89.34 | 44.97 |
| mGPT-1.3B + SCRIPT | 16.59 | 9.11 | 39.31 | 52.68 | 34.77 | 80.82 | 89.95 | 46.18 |
| Task | Lang | Example |
| KoCommonGen | Ko | Input: {있, 선로, 길, 옆, 열차 } Gold Label: 길 옆의 선로 에 열차가 있다. KoGPT2: 선로가 길 옆의 길 옆에 열차가 세워져 있다. KoGPT2 + SCRIPT : 열차들이 길 옆의 선로 에 있다. |
| En | Input: {be, tracks, road, beside, train } Gold Label: There is a train on the tracks beside the road. KoGPT2: The train is parked beside the track beside the road. KoGPT2 + SCRIPT : The trains are on the tracks beside the road. | |
| Kor-Learner | Ko | Input: 그리고 가장 중요한 영향은 그 앞으로 그 여행으로 이전보다 훨씬 더 ‘처음’ 을 접할 거다 . Gold Label: 그리고 가장 중요한 영향은 앞으로 여행으로 이전보다 훨씬 더 ‘처음’ 을 접할 것이라는 사실이다 . KoGPT2: 그리고 가장 중요한 영향을 그 앞으로 그 여행으로 이전보다 훨씬 더 ‘처음’ 을 접할 거다 . KoGPT2 + SCRIPT : 그리고 가장 중요한 영향은 그 앞으로 그 여행으로 이전보다 훨씬 더 ‘처음’ 을 접할 거라는 것이다 . |
| En | Input: And the most important impact would that, through that journey, they will encounter the ‘first’ much more than before. Gold Label: And the most important impact is the fact that, through future travels, they will encounter the ‘first’ much more than before. KoGPT2: And the most important impact would that, through that journey, they will encounter the ‘first’ much more than before. KoGPT2 + SCRIPT : And the most important impact is the thing that, through that journey, they will encounter the ‘first’ much more than before. | |
| Kor-Native | Ko | Input: 주말에 함께 *테니그 를 쳐여. Gold Label: 주말에 함께 테니스 를 쳐요. KoGPT2: 주말에 함께 *테니그 를 쳐요. KoGPT2 + SCRIPT : 주말에 함께 테니스 를 쳐요. |
| En | Input: Let’s play *tennig together on the weekend. Gold Label: Let’s play tennis together on the weekend. KoGPT2: Let’s play *tennig together on the weekend. KoGPT2 + SCRIPT : Let’s play tennis together on the weekend. |
| Task | Language | Example |
| XL-Sum | Korean | Input: 최종 목적은 2㎏ 정도의 ‘토양’ 표본을 상승선, 귀환선에 전달해 지구까지 가져오는 것이다 중국국가우주국(CNSA)은 달의 암석과 토양 표본을 수집해 지구로 가져오기 위해 출발한 무인 달 탐사선 ‘창어 5호’가 1일 밤 착륙에 성공했다고 2일 밝혔다. 창어 5호는 ‘폭풍의 바다’(Oceanus Procellarum)라는 지역 내 ‘몽스 륌케르’(Mons Rümker) 화산지대 북쪽에 안착했다. 이곳에서 며칠간 달 표면의 흙과 암석 표본 등을 수집한다. 창어 5호 탐사선에는 작업을 돕기 위한 카메라, 레이더, 드릴, 삽 등이 탑재돼있다. 최종 목적은 2㎏ 정도의 표토 표본을 상승선과 궤도선을 거쳐 귀환선에 전달해 지구까지 가져오는 것이다. 달의 토양 표본을 지구로 가져온 탐사선은 44년 전 1976년 옛 소련의 루나 24호가 마지막으로, 당시 200g의 토양을 지구로 옮기는 데 성공했다. 창어 5호 프로젝트 팀이 환호하는 모습 이날 달 착륙 모습은 일주일 전 발사 때와 달리 생중계 되지 않았다. 중국 TV 채널에서는 성공적인 착륙이 확인되고 나서야 정규 방송을 중단하고 이를 녹화 중계했다. 공개된 착륙 과정에는 탐사선의 다리가 달의 먼지 쌓인 표면에 그림자를 드리우는 장면 등이 포함됐다. … KoGPT2: 중국 국가우주국이 달 착륙에 성공한 창어 6호 달 착륙선에 탑재된 카메라와 레이더를 통해 달 표면 표본을 지구까지 운반했다. KoGPT2 + SCRIPT : 중국의 달 탐사 프로젝트가 성공적으로 마무리됐다. |
| English | Input: The primary goal is to bring approximately 2 kg of lunar soil samples back to Earth by transferring them from the ascent and return modules. The China National Space Administration (CNSA) announced on the 2nd that its unmanned lunar probe, Chang’e-5, successfully landed on the night of the 1st to collect lunar rock and soil samples to return to Earth. Chang’e-5 has landed in the volcanic area north of Mons Rümker within the region known as Oceanus Procellarum. Over the next few days, it will collect samples of lunar soil and rock. Equipped with cameras, radar, drills, and shovels to aid in its operations, the ultimate goal of Chang’e-5 is to gather about 2 kg of surface samples, which will be transferred from the ascent and orbital modules to the return module for their journey back to Earth. The last mission to bring lunar soil samples to Earth was the Soviet Union’s Luna 24 in 1976, which successfully transported 200 g of lunar soil back to Earth. On the day of the landing, the Chang’e-5 team celebrated. Unlike the launch, the landing was not broadcast live, and Chinese TV channels interrupted regular programming to air recorded footage after confirming a successful landing. The released landing process included images of the lander casting a shadow on the dusty lunar surface. … Gold Label: China has landed another probe on the surface of the moon. KoGPT2: The China National Space Administration successfully transported lunar surface samples to Earth using the camera and radar aboard the Chang’e 6 lunar lander. KoGPT2 + SCRIPT : China’s lunar exploration project has been successfully completed. |
| Model | Embedding Layer | Transformer Stacks | Restoration Layer |
| BERT | - | ||
| BERT + SCRIPT | ) | - | |
| KOMBO |
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