Web-scale Surface and Syntactic n-gram Features for Dependency Parsing
Table 3: Correct attachments by gold argument pos tag and the percentage of the overall error reduction over wsj section 22 for the baseline and combined systems in Table 2.
['Tag', 'Freq', 'base', 'comb', '%']
The most substantial gains come in nominal and prepositional phrases – known weaknesses for parsers, and the categories where syntactic n-gram features alone fare worst. However, the system finds less improvement in coordinators, determiners, and cardinal numbers, all of which are also components of noun phrases. This shows the difficulty of correctly identifying a head noun in a nominal to attach modifiers to, and the general difficulty of representing and parsing coordination.