We explore the use of segments learnt using Byte Pair Encoding (referred to as BPE units) as basic units for statistical machine translation between related languages and compare it with orthographic syllables, which are currently the best performing basic units for this translation task. BPE identifies the most frequent character sequences as basic units, while orthographic syllables are linguistically motivated pseudo-syllables. We show that BPE units outperform orthographic syllables as units of translation, showing up to 11 increase in BLEU scores. In addition, BPE can be applied to any writing system, while orthographic syllables can be used only for languages whose writing systems use vowel representations. We show that BPE units outperform word and morpheme level units for translation involving languages like Urdu, Japanese whose writing systems do not use vowels (either completely or partially). Across many language pairs, spanning multiple language families and types of writing systems, we show that translation with BPE segments outperforms orthographic syllables, especially for morphologically rich languages.
The first approach involves into the target languages. This can done by transliterating the untranslated words in a post-processing step @cite_33 @cite_32 , a technique generally used for handling named entities in SMT. However, transliteration candidates cannot be scored and tuned along with other features used in the SMT system. This limitation can be overcome by integrating the transliteration module into the decoder @cite_4 , so both translation and transliteration candidates can be evaluated and scored simultaneously. This also allows transliteration translation choices to be made.
@cite_32 @cite_33 @cite_4
2117717100 2139604620
We propose several techniques for improving statistical machine translation between closely-related languages with scarce resources. We use character-level translation trained on n-gram-character-aligned bitexts and tuned using word-level BLEU, which we further augment with character-based transliteration at the word level and combine with a word-level translation model. The evaluation on Macedonian-Bulgarian movie subtitles shows an improvement of 2.84 BLEU points over a phrase-based word-level baseline. We present a novel approach to integrate transliteration into Hindi-to-Urdu statistical machine translation. We propose two probabilistic models, based on conditional and joint probability formulations, that are novel solutions to the problem. Our models consider both transliteration and translation when translating a particular Hindi word given the context whereas in previous work transliteration is only used for translating OOV (out-of-vocabulary) words. We use transliteration as a tool for disambiguation of Hindi homonyms which can be both translated or transliterated or transliterated differently based on different contexts. We obtain final BLEU scores of 19.35 (conditional probability model) and 19.00 (joint probability model) as compared to 14.30 for a baseline phrase-based system and 16.25 for a system which transliterates OOV words in the baseline system. This indicates that transliteration is useful for more than only translating OOV words for language pairs like Hindi-Urdu.