Accurate Collocation Extraction Using a Multilingual Parser

Proceedings of the 21st International Conference on Computational Linguistics and 44th Annual Meeting of the ACL, pages 953–960, Sydney, July 2006. c⃝2006 Association for Computational Linguistics Accurate Collocation Extraction Using a Multilingual Parser Violeta Seretan Language Technology Laboratory University of Geneva 2, rue de Candolle, 1211 Geneva Violeta.Seretan@latl.unige.ch Eric Wehrli Language Technology Laboratory University of Geneva 2, rue de Candolle, 1211 Geneva Eric.Wehrli@latl.unige.ch Abstract This paper focuses on the use of advanced techniques of text analysis as support for collocation extraction. A hybrid system is presented that combines statistical meth- ods and multilingual parsing for detecting accurate collocational information from English, French, Spanish and Italian cor- pora. The advantage of relying on full parsing over using a traditional window method (which ignores the syntactic in- formation) is first theoretically motivated, then empirically validated by a compara- tive evaluation experiment. 1 Introduction Recent computational linguistics research fully ac- knowledged the stringent need for a systematic and appropriate treatment of phraseological units in natural language processing applications (Sag et al., 2002). Syntagmatic relations between words — also called multi-word expressions, or “id- iosyncratic interpretations that cross word bound- aries” (Sag et al., 2002, 2) — constitute an im- portant part of the lexicon of a language: accord- ing to Jackendoff (1997), they are at least as nu- merous as the single words, while according to Mel’ˇcuk (1998) they outnumber single words ten to one. Phraseological units include a wide range of phenomena, among which we mention compound nouns (dead end), phrasal verbs (ask out), idioms (lend somebody a hand), and collocations (fierce battle, daunting task, schedule a meeting). They pose important problems for NLP applications, both text analysis and text production perspectives being concerned. In particular, collocations1 are highly problem- atic, for at least two reasons: first, because their linguistic status and properties are unclear (as pointed out by McKeown and Radev (2000), their definition is rather vague, and the distinction from other types of expressions is not clearly drawn); second, because they are prevalent in language. Mel’ˇcuk (1998, 24) claims that “collocations make up the lions share of the phraseme inventory”, and a recent study referred in (Pearce, 2001) showed that each sentence is likely to contain at least one collocation. Collocational information is not only useful, but also indispensable in many applications. In ma- chine translation, for instance, it is considered “the key to producing more acceptable output” (Orliac and Dillinger, 2003, 292). This article presents a system that extracts ac- curate collocational information from corpora by using a syntactic parser that supports several lan- guages. After describing the underlying method- ology (section 2), we report several extraction re- sults for English, French, Spanish and Italian (sec- tion 3). Then we present in sections 4 and 5 a com- parative evaluation experiment proving that a hy- brid approach leads to more accurate results than a classical approach in which syntactic information is not taken into account. 2 Hybrid Collocation Extraction We consider that syntactic analysis of source cor- pora is …

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