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<Paper uid="C96-1053">
  <Title>Lexical Information for Determining Japanese Unbounded Dependency</Title>
  <Section position="3" start_page="0" end_page="310" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> When analyzing long sentences with two or more predicates (i.e. compound and complex sentences), it is difficult to grasp the proper structure of sentences having a large nmnber of possible dependency (modifiermodifee relation) structures. This difficulty is more marked in Japanese than in English, since there are more syntactically ambiguous structures in Japanese.</Paragraph>
    <Paragraph position="1"> Tile Japanese language has few syntactic indicators for dividing sentences into phrases or clauses, unlike English with its relative pronouns and subordinate conjunctions. One of the most critical features of Japanese is that the difference between a phra~se and a clause is not cleat'. Even subjects or other obligatory elements of clauses are omitted very often when they aye indicated by contexts. In addition, the Japanese language does not have any parts of speech to clearly indicate either the beginning or end of a phrase or a clause.</Paragraph>
    <Paragraph position="2"> Another critical feature is that the Japanese language is an almost pure Head-final language, i.e., predicates and function words to signify the sentence structure appear at the end of the clause or sentence. This means that it is syntactically possible for all phrases or clauses that can modit) predicates to modify all other phrases or clauses that appear in the latter part of long sentences. null These syntactic characteristics of the Japanese language make it difficult to determine the dependency (modification) structure of hmg sentences. Simple parsing of Japanese long sentences inevitably produces a huge number of possible modification structures. A conventional bottom-up parsing method can reduce ambiguity in modification by local information in tim surface structure. However, this inclines toward an improper output, since the locally highest likelihood is sometimes low on the whole.</Paragraph>
    <Paragraph position="3"> To overcome this problem, several methods to predict the global structure of long sentences have been proposed. One is a top-down parsing method by matching the input sentence and the domain-specific patterns (Furuse et al., 1992). Improvements made by other researchers enabled this method to parse irregular, incomplete and multiplex patterns, by describing the domain-dependent patterns in the form of grammar (Doi, Muraki, et M., 1993).</Paragraph>
    <Paragraph position="4"> Another method employs global structure presumption to divide a sentence into clauses by utilizing general lexical information. It predicts the sentence structure prior to syntactic analysis only by utilizing domain-independent lexical information such as conjunctive particles, parallel expressions, theme transition, etc. (Mizuno et al., 1990; Kurohashi et al., 1992). Lexical Discourse Grammar (LDG) is one of the approaches with which a global structure of a long sentence is presumed by focusing on function words (Kamei et al, 1986; Doi et al., 1991). LDG assumes that Japanese function words, such as conjunctive partides (postpositions) located at the end of each clause, convey modMity, or propositional attitude, and suggest global structures of Japanese long sentences in cooperation with modality in predicates, especially within  auxiliary verbs. LDG can presume the inter-clausal dei)endency within Japanese sentences prior to syntactic and semantic alLalyses by utilizing tilt; difDrences of the encapsulating powers each ,\]apaiLese function word has, and by utilizing modification preference-between function words and predicates that reflects consistency (if lnodality reading or propositional attitude inte, rpretation. null LDG is effective in reducing the syntactic ambiguities, and it him alre~My been applied to a machine translation system. Ilowever, it has not claritied the level of tile encapsulation powers of Japanese flint:tion words or tile relation between modality and level. IIence we refined the concept of LDG, lmrticularly tile conjunction level of function words, and explain the outline of the refilled LDG in tilts paper. First, we present the encapsulation power of Japanese function words, which are classified into six levels. Second, we state moditication l)refi3renee of ,}apanese conjunctiw'. particles that reflects modality within them. Filmlly, we present evidence of tile h;vels of aaplnLese function words. We think that tile h;vels of clauses produce prosodic infbrmation, especially tlw location and h;ngth of pauses, which are influenced by tile sentence 51obal struchn'e. We atnalyzed the speech utterances of a professional new,~ announcer (male) and fonnd a correla,tion between a particle's encapsulating power and tile pause hmgt;h inserted ai'ter dm clause with a conjunctiw; i~ar rich;.</Paragraph>
  </Section>
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