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<Paper uid="E95-1043">
  <Title>petence and Performance in the Human Sentence</Title>
  <Section position="4" start_page="291" end_page="292" type="intro">
    <SectionTitle>
3 Implementation
</SectionTitle>
    <Paragraph position="0"> Although Gorrell proposes a general principle to guide initial attachment decisions (Simplicity: No vacuous structure building), and specifies the conditions under which &amp;quot;unconscious reanalysis&amp;quot; may occur, the model leaves unspecified the problem of how the-system may be implemented. Of particular interest is the problem of how the parser decides which relations to add to the set at each point in time, especially at disambiguating points.</Paragraph>
    <Section position="1" start_page="291" end_page="291" type="sub_section">
      <SectionTitle>
3.1 Lexical Representation
</SectionTitle>
      <Paragraph position="0"> The basic framework on which the implementation is built is similar to Tree Adjoining Grammar (Joshi et al 1975). Each lexical category is associated with a set of structural relations, which determine its lexical subtree. We call this set the subtree projection of that lexical category. For example, the subtree projection for verbs in the English grammar is as follows, where Lex is a variable which will be instantiated to the actual verb found in the input.</Paragraph>
      <Paragraph position="1"> {dom(S,NP), dom(S,VP), dom(VP,V), dom(V,Lex), prec(NP,VP) } Lexical categories are also associated with lists of left and right attachment sites. In the above case, NP, (which will correspond to the subject of the verb), will be unified with the left attachment site. If a transitive verb is found in the input, then the parser consults the verb's argument structure and creates a new right attachment site for an NP, asserting also that this new NP is dominated by VP and preceded by V.</Paragraph>
    </Section>
    <Section position="2" start_page="291" end_page="292" type="sub_section">
      <SectionTitle>
3.2 Attachment
</SectionTitle>
      <Paragraph position="0"> Simple attachment can be performed in two ways, which are defined below, where the term current tree description is intended to denote the the set of structural relations built up to that point in processing: Intuitively, left attachment may be thought of in terms of attaching the current tree description to the left corner of the projection of the new word, while right attachment corresponds to attaching the projection of the new word to the right corner a realignment of thematic and, on GB assumptions, case dependencies. These are examples of what Gorrell calls secondary relations, which are not subject to the monotonicity requirement.</Paragraph>
      <Paragraph position="1">  of the current tree description. They are equivalent to Abney's Attach-L and Attach respectively.</Paragraph>
    </Section>
  </Section>
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