8. The method of claim 1 wherein each of the plurality of tree-based structures is associated with a target language model score that depends on the tree-based structure and target language tokens associated with the tree-based structure.
8. The method of claim 1 wherein each of the plurality of tree-based structures is associated with a target language model score that depends on the tree-based structure and target language tokens associated with the tree-based structure. 9. The method of claim 8 wherein decoding the input sequence of source tokens includes combining target language model scores associated with a plurality of tree-based structures.