The purpose of the latent variable model in such previous work is to do max-translation decoding and training (Blunsom et al., 2008), or to eliminate the gap between heuristic extraction and decoding (Kääriäinen, 2009), instead of grammar induction as synchronous rules are still extracted by the heuristic two-step pipeline.
our interest lies in using latent variable model to learn synchronous grammar directly from sentence pairs.