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<Paper uid="P03-2029">
  <Title>Word Sense Disambiguation Using Pairwise Alignment</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> WSD has been recognized as one of the most important subjects in natural language processing, especially in machine translation, information retrieval, and so on (Ide and V'eronis, 1998). Most of previous supervised methods can be classified into two major ones; approach based on association, and approach based on selectional restriction. The former uses some words around a target word, represented by n-word window. The latter uses some syntactic relations, say, verb-object, including necessarily a target word.</Paragraph>
    <Paragraph position="1"> However, there are some words that one approach gets good result for them while another gets worse, and vice versa. For example, suppose that we want to distinguish between &amp;quot;go off or discharge&amp;quot; and &amp;quot;terminate the employment&amp;quot; as a sense of &amp;quot;fire&amp;quot;. Consider the sentence in Brown Corpus1: My Cousin Simmons carried a musket, but he had loaded it with bird shot, and as the officer came opposite him, he rose up behind the wall and fired.</Paragraph>
    <Paragraph position="2"> 1In this case, we consider only one sentential context for the simplicity.</Paragraph>
    <Paragraph position="3"> The words such as &amp;quot;musket&amp;quot;, &amp;quot;loaded&amp;quot; and &amp;quot;bird shot&amp;quot; would seem useful in deciding the sense of &amp;quot;fire&amp;quot;, and serve as clue to leading the sense to &amp;quot;go off or discharge&amp;quot;. It seems that there is no clue to another sense. For this case, an approach based on association is useful for WSD. However, an approach based on selectional restriction would not be appropriate, because these clues do not have the direct syntactic dependencies on &amp;quot;fire&amp;quot;. On the other hand, consider the sentence in EDR Corpus: Police said Haga was immediately fired from the force.</Paragraph>
    <Paragraph position="4"> The most significant fact is that &amp;quot;Haga&amp;quot; (a person's name) appears as the direct object of &amp;quot;fire&amp;quot;. A selectional restriction approach would use this clue appropriately, because there is the direct dependency between &amp;quot;fire&amp;quot; and &amp;quot;Haga&amp;quot;. However, an association approach would make an error in deciding the sense, because &amp;quot;Police&amp;quot; and &amp;quot;force&amp;quot; tend to be a noise, from the point of view of an unordered set of words. Generally, an association does not use a syntactic dependency, and a selectional restriction uses only a part of words appeared in a sentence.</Paragraph>
    <Paragraph position="5"> In this paper, we present a new method for WSD, which uses syntactic dependencies for a whole sentence as a clue. They contain both of all words included in a sentence and all syntactic dependencies in it. Our method is based on a technique of pair-wise alignment, and described in the following two sections. Using our method, we have gotten appropriate sense for various cases including above examples. In section 4, we describe our experimental result for WSD on some verbs in SENSEVAL-1 (Kilgarriff, 1998).</Paragraph>
  </Section>
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