Parsing Gapping Constructions Based on Grammatical and Semantic Roles (2020)

Abstract: A gapping construction consists of a coordinated structure where redundant elements are elided from all but one conjuncts. This paper proposes a method of parsing sentences with gapping to recover elided elements. The proposed method is based on constituent trees annotated with grammatical and semantic roles that are useful for identifying elided elements. Our method outperforms the previous method in terms of F-measure and recall.

## introduction a gapping construction consists of a coordinated structure where redundant elements are elided from all but one conjuncts. for example, we can elide the second redundant verb "ate" from the sentence "john ate bread, and mary ate rice." we need to recover elided elements to interpret sentences with gapping; however, little work has focused on developing such methods. this paper proposes a method of parsing sentences with gapping. our proposed method uses constituent trees annotated with grammatical and semantic tags and a special tag indicating gapped conjuncts. the method parses a sentence to obtain a tag-annotated constituent tree and analyzes gapping constructions using the resulting tree when it includes gapped conjuncts. the analysis is based on a sequence alignment algorithm using grammatical and semantic tags. an experiment shows that our method outperforms the previous method in terms of f-measure and recall. ## gapping construction this section first explains gapping constructions in the penn treebank @xcite , on which our proposed method is based, and summarizes the previous work on analyzing sentences with gapping. ## proposed method this section describes our proposed method, which parses gapping constructions. our method enables existing ptb-based parsers to identify correspondences between correlates and remnants. elided elements can be recovered by such correspondences as described in section 2.1. one difficulty in parsing gapping constructions is insufficient data for modeling such phenomena because their occurrence is rare. to mitigate this problem, our method learns not directly from correspondences between correlates and remnants, but from the following tags easily obtained from the ptb: ## experiment we conducted an experiment using the ptb to evaluate the performance of our proposed method. 7 we used the standard ptb training, development, and test data split (i.e., sections 02-21, 22, and 23, respectively) and the kitaev and klein parser @xcite foot_7 that can use bert @xcite . we trained the parsing model by simply replacing the training and pre. rec. f @xcite the last row in finally, we report the constituency parsing performance. ## conclusion this paper has proposed a method of parsing gapping constructions based on tag-annotated constituent trees. our proposed method is simple but effective. we believe that it will serve as a strong baseline for the task of parsing gapping constructions. in the future work, we will extend our method by replacing the simple role matching score with grammatical or semantic similaritybased measures to improve the alignment accuracy.