Automatically Constructing a Lexicon of Verb Phrase Idiomatic Combinations

Automatically Constructing a Lexicon of Verb Phrase Idiomatic Combinations Afsaneh Fazly Department of Computer Science University of Toronto Toronto, ON M5S 3H5 Canada afsaneh@cs.toronto.edu Suzanne Stevenson Department of Computer Science University of Toronto Toronto, ON M5S 3H5 Canada suzanne@cs.toronto.edu Abstract We investigate the lexical and syntactic flexibility of a class of idiomatic expres- sions. We develop measures that draw on such linguistic properties, and demon- strate that these statistical, corpus-based measures can be successfully used for dis- tinguishing idiomatic combinations from non-idiomatic ones. We also propose a means for automatically determining which syntactic forms a particular idiom can appear in, and hence should be in- cluded in its lexical representation. 1 Introduction The term idiom has been applied to a fuzzy cat- egory with prototypical examples such as by and large, kick the bucket, and let the cat out of the bag. Providing a definitive answer for what idioms are, and determining how they are learned and un- derstood, are still subject to debate (Glucksberg, 1993; Nunberg et al., 1994). Nonetheless, they are often defined as phrases or sentences that involve some degree of lexical, syntactic, and/or semantic idiosyncrasy. Idiomatic expressions, as a part of the vast fam- ily of figurative language, are widely used both in colloquial speech and in written language. More- over, a phrase develops its idiomaticity over time (Cacciari, 1993); consequently, new idioms come into existence on a daily basis (Cowie et al., 1983; Seaton and Macaulay, 2002). Idioms thus pose a serious challenge, both for the creation of wide- coverage computational lexicons, and for the de- velopment of large-scale, linguistically plausible natural language processing (NLP) systems (Sag et al., 2002). One problem is due to the range of syntactic idiosyncrasy of idiomatic expressions. Some id- ioms, such as by and large, contain syntactic vio- lations; these are often completely fixed and hence can be listed in a lexicon as “words with spaces” (Sag et al., 2002). However, among those idioms that are syntactically well-formed, some exhibit limited morphosyntactic flexibility, while others may be more syntactically flexible. For example, the idiom shoot the breeze undergoes verbal inflec- tion (shot the breeze), but not internal modification or passivization (?shoot the fun breeze, ?the breeze was shot). In contrast, the idiom spill the beans undergoes verbal inflection, internal modification, and even passivization. Clearly, a words-with- spaces approach does not capture the full range of behaviour of such idiomatic expressions. Another barrier to the appropriate handling of idioms in a computational system is their seman- tic idiosyncrasy. This is a particular issue for those idioms that conform to the grammar rules of the language. Such idiomatic expressions are indistin- guishable on the surface from compositional (non- idiomatic) phrases, but a computational system must be capable of distinguishing the two. For ex- ample, a machine translation system should trans- late the idiom shoot the breeze as a single unit of meaning (“to chat”), whereas this is not the case for the literal phrase shoot the bird. In this study, we …

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