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<Paper uid="W97-1302">
  <Title>Constraints and Defaults on Zero Pronouns in Japanese Instruction Manuals</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> From simple electrical appliances to complex computer systems, almost all machines are accompanied by instruction manuals. Since recently there are many machines whose operating procedures are complicated, we have much more trouble in many cases including translating their manuals into other languages, maintaining consistency between the description in manuals and the actual behavior of the machines. To solve these problems, we have to have a computer assisted system for processing manual sentences. In processing instruction manuals written in Japanese, however, it is problematic that almost all subjects are omitted. They are called &amp;quot;zero subjects.&amp;quot; For example, machine translation systems have to supply appropriate subjects to translate sentences. Therefore, we have focused on anaphora resolution of zero subjects in Japanese manual sentences. Mori et al.(Mori and Nakagawa, 1996) show that properties of Japanese conditionals can be used to resolve them. In this paper, we propose new constraints and defaults based on properties of linguistic expressions, which are useful to estimate omitted subjects in addition to the constraints and defaults proposed by Mori et al.</Paragraph>
    <Paragraph position="1"> A large number of researchers have come to grip with the method of understanding some types of text including instruction manuals(Abe et al., 1988; Nomura, 1992; Eugenio, 1992). One of the most important matters of concern in these types of system is how we can resolve ambiguities in semantic representations and fill underspecified parts of them. Generally speaking, almost all systems described above take the following scheme. Firstly, each sentence in a text is translated into a semantic representation. In this process, the system uses only non-defeasible syntactic and semantic constraints.</Paragraph>
    <Paragraph position="2"> This way of analysis is known as the Nondefeasibility Thesis(Kameyama, 1995). Secondly, all of undetermined parts of the semantic representation are filled or settled by some kind of inferences based on the domain knowledge.</Paragraph>
    <Paragraph position="3"> This type of method, which uses a large amount of domain knowledge, seems to be dominant from the viewpoint of disambiguation. Moreover it scarcely depends on the language in use because the way of disambiguation is based on the inference with a certain knowledge base. On the other hand, in order to use this method, we have to prepare the amount of knowledge being large enough to cope with various types of described objects. Unfortunately, so far we have not had such a commonsense knowledge base.</Paragraph>
    <Paragraph position="4"> One of the ways to get rid of this situation is to adopt some knowledge which is independent of any particular domain. As such a kind of knowledge, we pay attention to pragmatic constraints, which have not been used sufficiently in the former methods.</Paragraph>
    <Paragraph position="5"> We expect that owing to pragmatic constraints the ambiguity in manual sentences would be resolved to some extent not in the process of inference but in the process of the translation of manual sentences into semantic representations.</Paragraph>
    <Paragraph position="6"> We do not commit ourselves to the domain specific knowledge, but use some ontological knowledge of ordinary manuals. For example, the correspondence of objects in the manual sentences to the objects in linguistic constraints, namely linguistic roles like the speaker, the hearer, and so on. Note that the ontology in this paper does not refer to all of the objects in the world described by manuals, like a certain part of machine. Aiming at independence from the domain knowledge of objects, we adopt one of general ontologies which is applicable to almost all manuals.</Paragraph>
    <Paragraph position="7"> Now we have to define the term 'SUBJECT' we used in this paper. Since our final goal is the determination of &amp;quot;the main participant&amp;quot; which is omitted, both of the term 'subject' and the term 'agent' are not suitable for referring to the omitted objects.</Paragraph>
    <Paragraph position="8"> For example, in a sentence in passive voice, the sub-ject corresponds to not the agent(namely the main participant), but the patient. Moreover, there are several types of sentences whose subjects are main participants even if they are not agents, like the description of states, attributes and so on. Therefore, we use the term 'SUBJECT' to denote the main participant of the sentence, namely ether the agent or the surface subject(in the case where the agent is not defined).</Paragraph>
  </Section>
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