Although parallel corpora are essential language resources for many NLP tasks, they are rare or even not available for many language pairs. Instead, comparable corpora are widely available and contain parallel fragments of information that can be used applications like statistical machine translations. In this research, we propose a generative LDA based model for extracting parallel fragments from comparable documents without using any initial parallel data or bilingual lexicon. The experimental results show significant improvement if the extracted sentence fragments generated by the proposed method are used in addition to an existing parallel corpus in an SMT task. According to human judgment, the accuracy of the proposed method for an English-Persian task is about 66%. Also, the OOV rate for the same task is reduced by 28%.
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