Non-Deterministic Oracles for Unrestricted Non-Projective Transition-Based Dependency Parsing
Anders J. Björkelund, Joakim Nivre · 2015
We study non-deterministic oracles for training non-projective beam search parsers with swap transitions.We map out the spurious ambiguities of the transition system and present two non-deterministic oracles as well as a static oracle that minimizes the number of swaps.An evaluation on 10 treebanks reveals that the difference between static and non-deterministic oracles is generally insignificant for beam search parsers but that non-deterministic oracles can improve the accuracy of greedy parsers that use swap transitions.