K-Best A* Parsing.

A* parsing makes 1-best search efficient by suppressing unlikely 1-best items. Existing k -best extraction methods can efficiently search for top derivations, but only after an exhaustive 1-best pass. We present a unified algorithm for k -best A* parsing which preserves the efficiency of k -best extraction while giving the speed-ups of A* methods. Our algorithm produces optimal k -best parses under the same conditions required for optimality in a 1-best A* parser. Empirically, optimal k -best lists can be extracted significantly faster than with other approaches, over a range of grammar types.