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<Paper uid="P00-1068">
  <Title>Diagnostic Processing of Japanese for Computer-Assisted Second Language Learning</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> In the recent classroom of second language learning, communicative approach(H.G. Widdowson, 1977) is promoted in which it matters for the students to become aware of the language use, i.e. the functionality of language usage and it's dependence on the situations and the contexts of communication.</Paragraph>
    <Paragraph position="1"> In order to achieve the objective according to \constructivistic&amp;quot; point of view of learning (T.M.Du y et al., 1991), the students are encouraged to produce sentences by themselves in various situations and contexts and guided to recognize by themselves the erroneous or inappropriate functions of their misused expressions. null We have already proposed a Computer-Assisted Language Learning(CALL) system (N.Kato et al., 1997) which provides the students with sample texts promoting their reflection on the errors and inappropriateness, detected by a diagnostic parser, of the sentences composed by the students lling the blanks set up in the given contexts and situations. In this paper we report on prototyping the diagnostic parser implemented using LTAG formalism as a component of the system. null LTAG(Lexicalized Tree Adjoining Grammar) is a lexicalized grammatical formalism (XTAG Research Group, 1995). For ease of diagnosing the erroneous sentences composed by the students, lexicalized type of grammars seemed most suitable. Comparing HPSG(Head-driven Phrase Structure Grammar) (C.Pollard et al., 1994) and LTAG, the well-known two (almost-)lexicalized grammars, LTAG looked more simple and especially convenient for sentence generation necessary in diagnosis. LTAG systematically associates an elementary tree structure with a lexical anchor and the structure is embedded in the corresponding lexical item. Associated with each of the external nodes of the embedded tree structure are feature structures such as inflection, case information, head symbol, semantic constraints as well as a di erence list for surface expressions. These features have their origin in the anchored lexical item.</Paragraph>
    <Paragraph position="2"> The feature information can, moreover, include the knowledge of situated language use.</Paragraph>
    <Paragraph position="3"> Appearance of the features at the external nodes of the lexical items greatly facilitates generation of local phrases which is indispensable in diagnostic parsing. These are the reason why we employed LTAG.</Paragraph>
    <Paragraph position="4"> Preference of uni cation to all-procedural handling excluded the so-called \ dependency grammar &amp;quot;(M.Nagao, 1996).</Paragraph>
  </Section>
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