Research in example-based machine translation (EBMT) has been hampered by the lack of efficient tree alignment algorithms for bilingual corpora. This paper describes an alignment algorithm for EBMT whose running time is quadratic in the size of the input parse trees. The algorithm uses dynamic programming to score all possible matching nodes between structure-sharing trees or forests. We describe the algorithm, various optimizations, and our implementation.
['Adam Meyers', 'Roman Yangarber', 'Ralph Grishman']
Alignment of shared forests for bilingual corpora