Utilizing Extra-Sentential Context for Parsing

Syntactic consistency is the preference to reuse a syntactic construction shortly after its appearance in a discourse. We present an analysis of the WSJ portion of the Penn Treebank, and show that syntactic consistency is pervasive across productions with various lefthand side nonterminals. Then, we implement a reranking constituent parser that makes use of extra-sentential context in its feature set. Using a linear-chain conditional random field, we improve parsing accuracy over the generative baseline parser on the Penn Treebank WSJ corpus, rivalling a similar model that does not make use of context. We show that the context-aware and the context-ignorant rerankers perform well on different subsets of the evaluation data, suggesting a combined approach would provide further improvement. We also compare parses made by models, and suggest that context can be useful for parsing by capturing structural dependencies between sentences as opposed to lexically governed dependencies.

• Type: Journal
• Year: 2010
• Where: EMNLP
• Authors: Jackie Chi Kit Cheung, Gerald Penn
• Keywords: EMNLP 2010, Generative Baseline Parser, Natural Language Processing, Penn Treebank, Penn Treebank WSJ