Clausal parsing helps data-driven dependency parsing: Experiments with Hindi
Samar Husain, Phani Harsha Gadde, Joakim Nivre, Rajeev Sangal · International Joint Conference on Natural Language Processing · 2011
This paper investigates clausal data-driven de- pendency parsing. We first motivate a clause as the minimal parsing unit by correlating in- ter- and intra-clausal relations with relation type, depth, arc length and non-projectivity. This insight leads to a two-stage formulation of parsing where intra-clausal relations are identified in the 1 st stage and inter-clausal rela- tions are identified in the 2 nd stage. We com- pare two ways of implementing this idea, one based on hard constraints (similar to the one used in constraint-based parsing) and one based on soft constraints (using a kind of pars- er stacking). Our results show that the ap- proach using hard constraints seems most promising and performs significantly better than single-stage parsing. Our best result gives significant increase in LAS and UAS, respec- tively, over the previous best result using sin- gle-stage parsing.