A toolkit for visualizing the coherence of tree-based reordering with word-alignments

Tree-based reordering constitutes an important motivation for the increasing interest in syntax-driven machine translation. It has often been argued that tree-based reordering might provide a more effective approach for bridging the word-order differences between source and target sentences. One major approach (known as Inversion Transduction Grammar) allows permuting the order of the subtrees dominated by the children of any node in the tree. In practice, it has often been observed that the word-alignments usually cohere only to a certain degree with this kind of tree-based reordering, i.e., there are cases of word-alignments that cannot be fully explained with tree-based reordering when the tree is fixed a priori. This paper describes a toolkit for visualizing alignment graphs that consist of a word-alignment together with a source or target tree. More importantly, the toolkit provides a facility for visualizing the coherence of word-alignment with tree-based reordering, highlighting nodes and word-alignments that are incompatible with one another. The tool allows visualizing the tree-based reordered source/target string as well as the reordered tree