Left-corner Methods for Syntactic Modelingwith Universal Structural Constraints
Table 4.5: Parsing results on CoNLL X and 2007 test sets with no stack depth bound (unlabeled attachment scores).
['[EMPTY]', '[BOLD] Arc-standard', '[BOLD] Arc-eager', '[BOLD] Left-corner  [BOLD] full', '[BOLD] Left-corner  [BOLD] limited']
Again, the overall tendency is the same as the English experiment. The arc-eager performs the best except Arabic. In some languages (e.g., Bulgarian, English, Spanish, and Swedish), the left-corner (full) performs better than the arc-standard, while the average score is 1.1 point below. This difference and the average difference between the arc-eager and the arc-standard (85.8 vs. 84.6) are both statistically significant (p < 0.01, the McNemar test). We can thus conclude that our left-corner parser is not stronger than the other state-of-the-art parsers even with rich features.