BBN System Description for WMT10 System Combination Task

BBN submitted system combination outputs for Czech-English, German-English, Spanish-English, French-English, and AllEnglish language pairs. All combinations were based on confusion network decoding. An incremental hypothesis alignment algorithm with flexible matching was used to build the networks. The bi-gram decoding weights for the single source language translations were tuned directly to maximize the BLEU score of the decoding output. Approximate expected BLEU was used as the objective function in gradient based optimization of the combination weights for a 44 system multi-source language combination (All-English). The system combination gained around 0.42.0 BLEU points over the best individual systems on the single source conditions. On the multi-source condition, the system combination gained 6.6 BLEU points.