A Comparison of Pivot Methods for Phrase-Based Statistical Machine Translation
Masao Utiyama, Hitoshi Isahara · 2007
We compare two pivot strategies for phrase-based statistical machine transla-tion (SMT), namely phrase translation and sentence translation. The phrase translation strategy means that we di-rectly construct a phrase translation ta-ble (phrase-table) of the source and tar-get language pair from two phrase-tables; one constructed from the source language and English and one constructed from En-glish and the target language. We then use that phrase-table in a phrase-based SMT system. The sentence translation strat-egy means that we first translate a source language sentence into n English sen-tences and then translate these n sentences into target language sentences separately. Then, we select the highest scoring sen-tence from these target sentences. We con-ducted controlled experiments using the Europarl corpus to evaluate the perfor-mance of these pivot strategies as com-pared to directly trained SMT systems. The phrase translation strategy signifi-cantly outperformed the sentence transla-tion strategy. Its relative performance was 0.92 to 0.97 compared to directly trained SMT systems.