Statistical parsing with an automatically-extracted tree adjoining grammar

We discuss the advantages of lexicalized tree-adjoining grammar as an alternative to lexicalized PCFG for statistical parsing, describing the induction of a probabilistic LTAG model from the Penn Treebank and evaluating its parsing performance. We find that this induction method is an improvement over the EM-based method of (Hwa, 1998), and that the induced model yields results comparable to lexicalized PCFG.