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<Paper uid="C94-2127">
  <Title>Bottom-Up Earley Deduction</Title>
  <Section position="6" start_page="800" end_page="807" type="concl">
    <SectionTitle>
5 Conclusion and thlture Work
</SectionTitle>
    <Paragraph position="0"> We have proposed bottom-up Earley deduction as a useful alternative to the top-down methods which require subsumption checking and restriction to avoid prediction loops.</Paragraph>
    <Paragraph position="1"> The proposed method should be improved in two directions. The first is that the lookup predi(:ate should not have to be specified by the user, but automatically inferred from the program.</Paragraph>
    <Paragraph position="2"> The second problem is that all non-unit clauses of tile program are added to the chart. The addition of non-unit clauses should be made dependent on the goal and the base cases in order to go from a purely bottora-up algorithm to a directed algorithm that combines the advantages of top-down and bottom-up processing. It has been repeatedly noted \[8, 17, 1\] that directed methods are more efficient than pure top-down or bottom-up methods. However, it is not clear how well the directed methods are applicable to grammars which do not depend on concatenation and have no unique 'left cornet&amp;quot; which should be connected to the start symbol.</Paragraph>
    <Paragraph position="3"> It remains to I)e seeit how bottom-up Barley deduction compares with (and can be combined with) the improved top-down Barley deduction of l)hrre \[3\], Johnson \[7\] mud Neumann \[91, and to head-driven methods with well-formed substring tables \[1\], and which methods are best suited for which kinds of problems (e.g. parsing, generation, noisy input, incremental processing etc.).</Paragraph>
  </Section>
class="xml-element"></Paper>