In these conditions, the language modeling and ordering assumptions of most MT models are unwarranted, so we instead use a simple bag-of-words translation model based only on co-occurrence: IBM Model 1 (Brown et al., 1993) with a Dirichlet prior over translation distributions, as learned by fast align (Dyer et al., 2013).
2 for each pseudoterm, we learn a translation distribution over possible target words.