High-quality parallel data is crucial for a range of multilingual applications, from tuning and evaluating machine translation systems to cross-lingual annotation projection. Unfortunately, automatically obtained parallel data (which is available in relative abundance) tends to be quite noisy. To obtain high-quality parallel data, we introduce a crowdsourcing paradigm in which workers with only basic bilingual proficiency identify translations from an automatically extracted corpus of parallel microblog messages. For less than $350, we obtained over 5000 parallel segments in five language pairs. Evaluated against expert annotations, the quality of the crowdsourced corpus is significantly better than existing automatic methods: it obtains an performance comparable to expert annotations when used in MERT tuning of a microblog MT system; and training a parallel sentence classifier with it leads also to improved results. The crowdsourced corpora will be made available in http://www.cs.cmu.edu/ ~lingwang/microtopia/.
['Wang Ling', 'Luís Marujo', 'Chris Dyer', 'Alan W. Black', 'Isabel Trancoso']
Crowdsourcing High-Quality Parallel Data Extraction from Twitter