Semantic Analysis of Japanese Noun Phrases - A New Approach to Dictionary-Based Understanding

Semantic Analysis of Japanese Noun Phrases : A New Approach to Dictionary-Based Understanding Sadao Kurohashi and Yasuyuki Sakai Graduate School of Informatics, Kyoto University Yoshida-honmachi, Sakyo, Kyoto, 606-8501, Japan kuro0i, kyoto-u, ac. jp Abstract This paper presents a new method of analyz- ing Japanese noun phrases of the form N1 no 5/2. The Japanese postposition no roughly cor- responds to of, but it has much broader us- age. The method exploits a definition of N2 in a dictionary. For example, rugby no coach can be interpreted as a person who teaches tech- nique in rugby. We illustrate the effectiveness of the method by the analysis of 300 test noun phrases. 1 Introduction The semantic analysis of Japanese noun phrases of the form N1 no N2 is one of the difficult prob- lems which cannot be solved by the current ef- forts of many researchers. Roughly speaking, Japanese noun phrase N1 no N2 corresponds to English noun phrase N2 of N1. However, the Japanese postposition no has much broader us- age than of as follows: watashi 'I' no kuruma 'car' tsukue 'desk' no ashi 'leg' gray no seihuku 'uniform' possession whole-part modification senmonka 'expert' no chousa 'study' agent rugby no coach subject yakyu 'baseball' no senshu 'player' category kaze 'cold' no virus result ryokou 'travel' no jyunbi 'preparation' purpose toranpu 'card' no tejina 'trick' instrument The conventional approach to this problem was to classify semantic relations, such as pos- session, whole-part, modification, and others. Then, classification rules were crafted by hand, or detected from relation-tagged examples by a machine learning technique (Shimazu et al., 1987; Sumita et al., 1990; Tomiura et al., 1995; Kurohashi et al., 1998). The problem in such an approach is to set up the semantic relations. For example, the above examples and their classification came from the IPA nominal dictionary (Information- Technology Promotion Agency, Japan, 1996). Is it possible to find clear boundaries among subject, category, result, purpose, instrument, and others? No matter how fine-grained rela- tions we set up, we always encounter phrases which are on the boundary or belong to two or more relations. This paper proposes a completely different approach to the task, which exploits semantic role information of nouns in an ordinary dictio- nary. 2 Semantic Roles of Nouns The meaning of a word can be recognized by the relationship with its semantic roles. In the case of verbs, the arguments of the predicates constitute the semantic roles, and a consider- able number of studies have been made. For example, the case grammar theory is a semantic valence theory that describes the logical form of a sentence in terms of a predicate and a series of case-labeled arguments such as agent, object, location, source, goal (Fillmore, 1968). Further- more, a wide-coverage dictionary describing se- mantic roles of verbs in machine readable form has been constructed by a great deal of labor (Ikehara et al., 1997). Not only verbs, but also nouns can have se- mantic roles. For example, coach is a coach of …

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