Following the broad shift in the field from finite state transducers to grammar transducers (Chiang, 2007), recent approaches to phrase-based alignment have used synchronous grammar formalisms permitting polynomial time inference (Wu, 1997;Cherry and Lin, 2007;Zhang et al., 2008b;Blunsom et al., 2008).
markov chain monte Carlo sampling allows us to perform inference for the model described in 4.1 without restricting the infinite space of possible translation rules.