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<Paper uid="P91-1013">
  <Title>LR RECURSIVE TRANSITION NETWORKS FOR EARLEY AND TOMITA PARSING</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1. INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> Ambiguous context-free grammars (CFGs) are currently used in the syntactic and semantic processing of natural language. For efficient parsing, two major computational methods are used. The first is Earley's algorithm (Earley, 1970), which merges parse trees to reduce the computational dependence on input sentence length from exponential to cubic cost. Numerous variations on Earley's dynamic programming method have developed into a family of chart parsing (Winograd, 1983) algorithms. The second is Tomita's algorithm (Tomita, 1986), which generalizes Knuth's (Knuth, 1965) and DeRemer's (DeRemer, 1971) computer language LR parsing techniques. Tomita's algorithm augments the LR parsing &amp;quot;set of items&amp;quot; construction with Earley's ideas.</Paragraph>
    <Paragraph position="1"> What is not currently appreciated is the continuity between these apparently distinct computational methods.</Paragraph>
    <Paragraph position="2"> * Tomita has proposed (Tomita, 1985) constructing his algorithm from Earley's parser, instead of DeRemer's LR parser. In fact, as we shall show, Earley's algorithm may be viewed as one form of LR parsing.</Paragraph>
  </Section>
class="xml-element"></Paper>