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<Paper uid="P84-1102">
  <Title>Disambiguating Grammatically Ambiguous Sentences By Asking</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1. Introduction
</SectionTitle>
    <Paragraph position="0"> /~ F=rge number of techniques using semantic information have been deve!oped to resolve natural language ambiguity. However, not all ambiguity problems can be solved by those techniques at the current state of art. Moreover, some sentences are absolutely ambiguous, that is, even a human cannot disambiguate them.</Paragraph>
    <Paragraph position="1"> Therefore. it is important for the system to be capable of asking a user questions interactively to disambiguate a sentence.</Paragraph>
    <Paragraph position="2"> Here, we make an important condition that an user is neither a computer scientist nor a linguist. Thus, an user may ROt recognize an;, spec=al terms or notations like a tree structure, phrase structure grammar, etc.</Paragraph>
    <Paragraph position="3"> The first system to disambiguate sentences by asking interactively is perhaps a program called &amp;quot;disambiguator&amp;quot; in Kay's MINO system \[2\]. Although the disambiguation algorithm is not presented in \[2\], some basic ideas have been already implemented in the Kay's system 2. In this paper, we shall only deal with grammatical ambiguity, or in other words, syntactic ambiguity. Other umhiguity problems, such as word-sense ambiguity and referential ambiguity, are excluded.</Paragraph>
    <Paragraph position="4"> Suppose a system is given the sentence: &amp;quot;Mary saw a man with a telescope&amp;quot; and the system has a phrase structure grammar including the following rules &lt;a&gt; - &lt;g&gt;:  &lt;a&gt; S --&gt; NP + VP &lt;b&gt; S --&gt; NP + VP + PP &lt;c&gt; NP --&gt; *noun &lt;d&gt; NP --&gt; *det+ *noun &lt;e&gt; NP --&gt; NP + PP &lt;f&gt; PP --&gt; *prep + NP &lt;g&gt; VP --&gt; *verb + NP  The system would produce two parse trees from the input sentence (I. using rules &lt;b&gt;,&lt;c&gt;,&lt;g&gt;,&lt;d&gt;,&lt;f&gt;,&lt;d&gt;; II. using rules &lt;a&gt;,&lt;c&gt;,&lt;g&gt;,&lt;e&gt;,&lt;d&gt;,&lt;f&gt;,&lt;d&gt;). The difference is whether the preposition phrase &amp;quot;with a telescope&amp;quot; qualifies the noun phrase &amp;quot;a man&amp;quot; or the sentence &amp;quot;Mary saw a man&amp;quot;. This paper shall discuss on how to ask the user&amp;quot; to select his intended interpretation without showing any kind of tree structures or phrase structure grammar rules. Our desired questior~ for that  sentence is thus something like: 1) The action &amp;quot;Mary saw a man&amp;quot; takes place &amp;quot;with a telescope&amp;quot; 2) &amp;quot;a man&amp;quot; is &amp;quot;with a telescope&amp;quot;</Paragraph>
  </Section>
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