| Abstract | Via an oracle experiment, we show that the upper bound on accuracy of a CCG parser is significantly lowered when its search space is pruned using a supertagger, though the supertagger also prunes many bad parses. |
| CCG and Supertagging | CCG is a lexicalized grammar formalism encoding for each word lexical categories that are either basic (eg. |
| CCG and Supertagging | As can be inferred from even this small example, a key difficulty in parsing CCG is that the number of categories quickly becomes extremely large, and there are typically many ways to analyze every span of a sentence. |
| Experiments | We evaluated on CCGbank (Hockenmaier and Steedman, 2007), a rightmost normal-form CCG version of the Penn Treebank. |
| Experiments | :nce our combined model represents the best CCG rsing results under any setting. |
| Integrated Supertagging and Parsing | Even allowing for the observation of Fowler and Penn (2010) that our practical CCG is context-free, this problem still reduces to the construction of Bar-Hillel et al. |
| Introduction | Accurate and efficient parsing of Combinatorial Cat-egorial Grammar ( CCG ; Steedman, 2000) is a longstanding problem in computational linguistics, due to the complexities associated its mild context sensitivity. |
| Introduction | Even for practical CCG that are strongly context-free (Fowler and Penn, 2010), parsing is much harder than with Penn Treebank—style context-free grammars, with vast numbers of nonterminal categories leading to increased grammar constants. |
| Introduction | Where a typical Penn Treebank grammar may have fewer than 100 nonterminals (Hockenmaier and Steedman, 2002), we found that a CCG grammar derived from CCGbank contained over 1500. |
| Discussion | To contrast, consider CCG (Steedman, 2000), in which semantic parsing is driven from the lexicon. |
| Discussion | In DCS, we start with lexical triggers, which are more basic than CCG lexical entries. |
| Discussion | (2008) induces first-order formulae using CCG in a small domain assuming observed lexical semantics. |
| Experiments | Note that having lexical triggers is a much weaker requirement than having a CCG lexicon, and far easier to obtain than logical forms. |
| Introduction | CCG is one instantiation (Steedman, 2000), which is used by many semantic parsers, e.g., Zettlemoyer and Collins (2005). |