Lexical Semantics to Disambiguate Polysemous Phenomena of Japanese Adnominal Constituents

Lexical Semantics to Disambiguate Polysemous Phenomena of Japanese Adnominal Constituents Hitoshi Isahara and Kyoko Kanzaki Communications Research Laboratory 588-2 Iwaoka, Iwaoka-cho, Nishi-ku Kobe, Hyogo, 651-2401, Japan {isahara, kanzaki}~crl.go.jp Abstract We exploit and extend the Generative Lexicon The- ory to develop a formal description of adnominal constituents in a lexicon which can deal with linguis- tic phenomena found in Japanese adnominal con- stituents. We classify the problematic behavior into "static disambiguation" and "dynamic disambigua- tion" tasks. Static disambiguation can be done using lexical information in a dictionary, whereas dynamic disambiguation requires inferences at the knowledge representation level. 1 Introduction Natural language processing must disambiguate pol- ysemous constituents in the input sentences. A good description of information necessary for disambigua- tion in the lexicon is crucial in high quality NLP sys- tems. This paper discusses the treatment of linguis- tic phenomena in Japanese adnominM constituents and it focuses on how to generate the same semantic representation from different syntactic structures, and how to generate different semantic representa- tions from a semantically ambiguous sentence. We exploit and extend the Generative Lexicon Theory (Pustejovsky, 1995; Bouillon, 1996) to develop a for- mal description of adnominal constituents in a lexi- con which can offer a solution to these problems. We classify the problematic behavior of Japanese adnominal constituents into "static disambiguation" and "dynamic disambiguation" tasks. Whereas static disambiguation can be done using the lexical information in a dictionary, dynamic disambigua- tion needs inferences at the knowledge representa- tion level. This paper mainly discusses dynamic dis- ambiguation. 2 Classification of the Usage of Japanese Adnominal Constituents On consideration of the syntactic relations between adnominal constituents and their head nouns, we find that some adnominal constituents can appear both in the attributive and predicative positions (Sakuma, 1967; Martin, 1975; Makino and Tsutsui, 1986). However, some adjectives express different meanings when they appear in one or the other po- sition and some adjectives can appear only in one of these two positions (Hashimoto and Aoyama, 1992). We have classified the semantic relations between adnominal constituents and their modified nouns, based on whether the paraphrasing from attributive position to predicative position is possible or not. There are three possibilities: (Type A)A paraphrase can be made without changing the modifying relations semantically. Ad. + N -, N $~ (ga) Ad. (N is Ad.) Ad. = Adnominal constituent N = Head noun of noun phrase which is modified by Ad. (Type B) A paraphrase can be made only when a noun is restricted by its context: the presence of modifiers or determiners, e.g., articles. Ad. + N --* ~:¢)(sono) N F~ (wa) Ad. (that N is Ad.) (Type C) A paraphrase cannot be made at all, i.e., only the attributive position is available. Ad. + N --~ *none. We can classify semantic relations between ad- nominal constituents and their head nouns into three types by the use of paraphrase. Paraphrases exist for both Type A and Type B, however, a paraphrase cannot be made at all for Type C. This difference …

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