After filtering non-projective trees, we retain the one-best sequence (if one projective tree exists), or the original sequence otherwise.
where preordering aims to find an optimal (for SMT) permutation of source words for each source sentence, our objective is less ambitious, as we only intend to 'fix' a sufficiently large number of divergent patterns between the source and target languages, so as to increase the effectiveness of transfer at the model level.