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<Paper uid="P85-1035">
  <Title>Native: Learner: Native: Learner: Native: Learner: Native: Remember the s~ory of David and Goliath?</Title>
  <Section position="2" start_page="0" end_page="284" type="intro">
    <SectionTitle>
1. Introduction
</SectionTitle>
    <Paragraph position="0"> A language understanding program should be able to acquire new lexical items from context, forming for novel phrases their linguistic patterns and figuring out their conceptual meanings. The lexicon of a learning program should satisfy three requirements: Each lexical entry should (1) be learnable, (2) facilitate conceptual analysis, and (3) facilitate generation. In this paper we focus on the first two aspects.</Paragraph>
    <Section position="1" start_page="0" end_page="284" type="sub_section">
      <SectionTitle>
1.1 The Task Domain
</SectionTitle>
      <Paragraph position="0"> Two examples, which will be used throughout this paper, are given below. In the first dialogue the learner is introduced to an unknown phrase: take on. The words take and on are familiar to the learner, who also remembers the biblical story of David and Goliath. The program, modeling a language learner, interacts with a native speaker, as follows: * This work w~s made possible in part by s grant from the Keck Foundation.</Paragraph>
      <Paragraph position="1"> Native: Learner: Native: Learner: Jenny vant,ed ~o go punk, but, her father put, his toot dovu.</Paragraph>
      <Paragraph position="2"> He moved his foot dora? It, doen not, mike sense.</Paragraph>
      <Paragraph position="3"> No. He put his foot, dora.</Paragraph>
      <Paragraph position="4"> He put his foot dovu.</Paragraph>
      <Paragraph position="5"> He refused to let her go punk.</Paragraph>
      <Paragraph position="6"> A figurative phrase such as put one's fooc down is a linguistic pattern whose associated meaning cannot be produced from the composition of its constituents. Indeed, an interpretation of the phrase based on the meanings of its constituents often exists, but it carries a different meaning. The fact that this literal interpretation of the figurative phrase exists is a misleading clue in learning. Furthermore, the learner may not even notice that a novel phrase has been introduced since she is familiar with dram as well as with foot. Becker \[Becker?5\] has described a space of phrases ranging in generality from fixed proverbs such as charity begsns at, home through idioms such as Xay dove t,he tar and phrasal verbs such as put, up rich one's spouse and look up the name, to literal verb phrases such as sit, on she chair. He suggested employing a phrasal lexicon to capture this entire range o( language structures.</Paragraph>
    </Section>
    <Section position="2" start_page="284" end_page="284" type="sub_section">
      <SectionTitle>
1.2 Issues in Phrase AequLsition
</SectionTitle>
      <Paragraph position="0"> Three issues must be addressed when learning phrases in context.</Paragraph>
      <Paragraph position="1"> (I) Detecting failures: What are the indications that the initial interpretation of the phrase take him on as &amp;quot;to take a person to a location&amp;quot; is incorrect? Since all the words in the sentence are known, the problem is detected both as a conceptual discrepancy (why would he take his enemy anywhere?) and as a syntactic failure (the expected location of the assunied physical transfer is missing).</Paragraph>
      <Paragraph position="2"> (2) Determining scope and generality of patterns: The linguistic pattern of a phrase may be perceived by the learner at various levels of generalit~l. For example, in the second dialogue, incorrect generalizations could yield patterns accepting sentences such as: Her boss put his left foot down.</Paragraph>
      <Paragraph position="3"> He moved his foot dora.</Paragraph>
      <Paragraph position="4"> He put down his foot.</Paragraph>
      <Paragraph position="5"> He put dovn his leg.</Paragraph>
      <Paragraph position="6">  A decision is also required about the scope of the pattern (i.e., the tokens included in the pattern). For instance, the scope of the pattern in John put up with Mary could be (I) ?x:persoa put:verb up where with is associated with l'lmry or (2) ?x:persos put:verb up with ?y:persou, where with is associated with put up.</Paragraph>
      <Paragraph position="7"> Finding appropriate meanings: The conceptual meaning of the phrase must be extracted from the context which contains many concepts, both appropriate and inappropriate for hypothesis formation. Thus there must be strategies for focusing on appropriate elements in the context.</Paragraph>
    </Section>
    <Section position="3" start_page="284" end_page="284" type="sub_section">
      <SectionTitle>
1.3 The Program
</SectionTitle>
      <Paragraph position="0"> RINA \[Dyer85\] is a computer program designed to learn English phrases. It takes as input English sentences which may include unknown phrases and conveys as output its hypotheses about novel phrases. The pro~am consists of four components: (l) Phrasal lexicon: This is a list of phrases where each phrase is a declarative pattern-concept pair \[WilenskySl\].</Paragraph>
      <Paragraph position="1"> (2) Case-frame parser: In the parsing process, case-frame expectations are handled by spawning demons \[Dyer83\]. The parser detects comprehension failures which are used in learning.</Paragraph>
    </Section>
  </Section>
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