Finding Non-local Dependencies: Beyond Pattern Matching

We describe an algorithm for recovering non-local dependencies in syntactic dependency structures. The patternmatching approach proposed by Johnson (2002) for a similar task for phrase structure trees is extended with machine learning techniques. The algorithm is essentially a classifier that predicts a nonlocal dependency given a connected fragment of a dependency structure and a set of structural features for this fragment. Evaluating the algorithm on the Penn Treebank shows an improvement of both precision and recall, compared to the results presented in (Johnson, 2002).