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<Paper uid="C96-2137">
  <Title>Anaphora Resolution of Japanese Zero Pronouns with Deictic Reference</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> In all natural language, elements that can be easily deduced by the reader are frequently omitted from expressions in texts (Kuno, 1978). This phenomenon causes considerable problems in natural language processing systems. For example in a machine translation system, the system needs to recognize that elements which are not present in the source language, may become mandatory elements in the target language. In particular, the subject and object are often omitted in Japanese; whereas they are often mandatory in English.</Paragraph>
    <Paragraph position="1"> Thus, in Japanese-to-English machine translation systems, it is necessary to identify case elements omitted from the original Japanese (these are referred to as &amp;quot;zero pronouns&amp;quot;) for their translation into English expressions.</Paragraph>
    <Paragraph position="2"> Several methods have been proposed with regard to this problem (Kameyama, 1986) (Walker et al., 1990) (Yoshimoto, 1988) (Dousaka, 1994).</Paragraph>
    <Paragraph position="3"> When considering the application of these methods to a practical machine translation system for which the translation target area can not be limited, it is not possible to apply them directly, both because their precision of resolution is low as they only use limited information, and because the volume of knowledge that must be prepared betbrehand is so large.</Paragraph>
    <Paragraph position="4"> The zero pronouns that must be resolved by a machine translation system carl be classitied into 3 types; (a) zero pronouns with antecedents within the same sentence (intrasenteutial), (b) zero pronouns with antecedents elsewhere in the text (intersentential) and (c) zero pronouns with deictic reference (extrasentential). Regarding type (b), Nakaiwa and Ikehara (1992) proposed a method to determine the intersentential antecedents us-ing verbal semantic attributes. The rules used in this method are independent of the field of the source text. Therefore, anaphora resolution may be conducted with a relatively small volume of knowledge, making the proposed method very suitable for machine translation systems. Furthermore, for type (a), Nakaiwa and \[kehara(1995) proposed a method to determine the intrasententim antecedents of Japanese zero pronouns using semantic constraints such as verbal semantic attributes and pragmatic constraints such as types of conjunctions and modal expressions.</Paragraph>
    <Paragraph position="5"> In this paper, we propose a widely applicable method to determine the deictic referents of Japanese zero pronouns (type (c)) using not only semantic constraints to the c~es but also fln:ther semantic constraints such as verbal semantic attributes and pragmatic constraints such as modal expressions and types of conjunctions.</Paragraph>
  </Section>
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