Translating Hanja Historical Documents to Contemporary Korean and English

The Annals of Joseon Dynasty (AJD) contain the daily records of the Kings of Joseon, the 500-year kingdom preceding the modern nation of Korea. The Annals were originally written in an archaic Korean writing system, 'Hanja', and were translated into Korean from 1968 to 1993. The resulting translation was however too literal and contained many archaic Korean words; thus, a new expert translation effort began in 2012. Since then, the records of only one king have been completed in a decade. In parallel, expert translators are working on English translation, also at a slow pace and produced only one king's records in English so far. Thus, we propose H2KE, a neural machine translation model, that translates historical documents in Hanja to more easily understandable Korean and to English. Built on top of multilingual neural machine translation, H2KE learns to translate a historical document written in Hanja, from both a full dataset of outdated Korean translation and a small dataset of more recently translated contemporary Korean and English. We compare our method against two baselines: a recent model that simultaneously learns to restore and translate Hanja historical document and a Transformer based model trained only on newly translated corpora. The experiments reveal that our method significantly outperforms the baselines in terms of BLEU scores for both contemporary Korean and English translations. We further conduct extensive human evaluation which shows that our translation is preferred over the original expert translations by both experts and non-expert Korean speakers. * Equal contribution. Hanja 改淸州牧爲西原縣. 以 劇賊 胎生邑, 降號 也. Original Korean Translation (oKo) 청주목을 서원현으로 고쳤다. 극적 이 태생한 고을은 강호 하기 때문이다. Eng.) Cheongju-mok was renamed Seowon-hyeon. It is because the town gets gangho if geukjeok is born. Contemporary Korean Translation (cKo) 청주목을 서원현으로 고쳤다. 극악한 역적 이 태어난 고을이므로 읍호를 강등 한 것이다. Eng.) Cheongju-mok was renamed Seowon-hyeon. Since it is a town where a vicious traitor was born, the town was demoted .