First, we reinterpret the ad-hoc tree score in previous spanbased parsing work (Stern et al., 2017;Gaddy et al., 2018;Kitaev and Klein, 2018) as a joint distribution over the labels.
global decoding methods (Durrett and Klein, 2015;Lee et al., 2016) can incorporate non-local features and decode a tree with the maximum global score.