文章基本信息

标题：Unary Constraints for Efficient Context-Free Parsing
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作者：Nathan Bodenstab ; Kristy Hollingshead ; Brian Roark 等
期刊名称：Conference on European Chapter of the Association for Computational Linguistics (EACL)
出版年度：2011
卷号：2011
出版社：ACL Anthology
摘要：We present a novel pruning method for context-free parsing that increases efficiency by disallowing phrase-level unary productions in CKY chart cells spanning a single word. Our work is orthogonal to recent work on ¡°closing¡± chart cells, which has focused on multi-word constituents, leaving span-1 chart cells unpruned. We show that a simple discriminative classifier can learn with high accuracy which span-1 chart cells to close to phrase-level unary productions. Eliminating these unary productions from the search can have a large impact on downstream processing, depending on implementation details of the search. We apply our method to four parsing architectures and demonstrate how it is complementary to the cell-closing paradigm, as well as other pruning methods such as coarse-to-fine, agenda, and beam-search pruning.