Data-oriented parsing with discontinuous constituents and function tags

• Main Authors: Andreas van Cranenburgh, Remko Scha, Rens Bod
• Format: Article
• Language: English
• Published: Polish Academy of Sciences 2016-04-01
• Series: Journal of Language Modelling
• Subjects: discontinuous constituents; statistical parsing; tree-substitution grammar
• Online Access: https://jlm.ipipan.waw.pl/index.php/JLM/article/view/100

Statistical parsers are e ective but are typically limited to producing projective dependencies or constituents. On the other hand, linguisti- cally rich parsers recognize non-local relations and analyze both form and function phenomena but rely on extensive manual grammar development. We combine advantages of the two by building a statistical parser that produces richer analyses.  We investigate new techniques to implement treebank-based parsers that allow for discontinuous constituents. We present two systems. One system is based on a string-rewriting Linear Context-Free Rewriting System (LCFRS), while using a Probabilistic Discontinuous Tree Substitution Grammar (PDTSG) to improve disambiguation performance. Another system encodes the discontinuities in the labels of phrase structure trees, allowing for efficient context-free grammar parsing. The two systems demonstrate that tree fragments as used in tree-substitution grammar improve disambiguation performance while capturing non-local relations on an as-needed basis. Additionally, we present results of models that produce function tags, resulting in a more linguistically adequate model of the data. We report substantial accuracy improvements in discontinuous parsing for German, English, and Dutch, including results on spoken Dutch.