Fine-tuning a Subtle Parsing Distinction Using a Probabilistic Decision Tree: the Case of Postnominal “that” in Noun Complement Clauses vs. Relative Clauses

Fine-tuning a Subtle Parsing Distinction Using a Probabilistic Decision Tree: the Case of Postnominal "that" in Noun Complement Clauses vs. Relative Clauses Zineddine Tighidet Université Paris Cité F-75013 Paris, France tighidet.zineddine@gmail.com Nicolas Ballier CLILLAC-ARP and LLF, Université Paris Cité & CNRS F-75013 Paris France nicolas.ballier@u-paris.fr Abstract In this paper we investigated two different meth- ods to parse relative and noun complement clauses in English and resorted to distinct tags for their corresponding that as a relative pro- noun and as a complementizer. We used an algorithm to relabel a corpus parsed with the GUM Treebank using Universal Dependency. Our second experiment consisted in using Tree- Tagger, a Probabilistic Decision Tree, to learn the distinction between the two complement and relative uses of postnominal “that”. We investigated the effect of the training set size on TreeTagger accuracy and how representative the GUM Treebank files are for the two struc- tures under scrutiny. We discussed some of the linguistic and structural tenets of the learnabil- ity of this distinction. 1 Introduction English has relative clauses (the man that I saw) and noun complement clauses (the fact that I saw a man) that may have similar surface representa- tions (often the definite article, a noun, often im- mediately followed by that) but different structural properties (Ballier, 2004). For POS-tagging sys- tems based on trigrams, the distinction between these constructions can be challenging, not to men- tion the case of ambiguous sentences such as "the suggestion that he was advancing was ridiculous" (Huddleston, 1984).This is an issue for information retrieval, as conceptual argumentation makes heavy uses of noun complement clauses (Ballier, 2007), the governors of these noun complement clauses being "shell nouns" (Schmid, 2000). Complement taking nouns (Bowen, 2005) are crucial for the ex- pression of stance (Charles, 2007) in documents, which is why this distinction may matter more than is usually assumed. The Penn Treebank (Marcus et al., 1993) tagset (Santorini, 1990) does not make strict distinc- tions between the part-of-speech (POS) tag of "that" when used as a relative pronoun (WDT) or when used as a conjunction when complemen- tizing nouns: it uses IN when complementizing verbs or nouns. Even though the CLAWS8 1. (Uni- versity Centre for Computer Corpus Research on Language, 1995-2004) tagset encodes this distinc- tion with the CST2 and WPR3 tags, this tagger is not free and remains the property of the Uni- versity Centre for Computer Corpus Research on Language (UCREL). To the best of our knowledge, the precision and recall of these two tags (and their corresponding syntactic structures) have not been reported. Admitting POS-tagging systems have reached an overall satisfactory precision rate for standard English tagsets, we claim that this is not necessarily the case for tags that reflect such a subtle distinc- tion which may have very similar surface represen- tations. Discussing such POS-tags involves parsing issues of the that-clause that follows the noun. Our research question is mostly based on the ability of a system to identify noun complement clauses as apposed to …

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