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<Paper uid="C90-3033">
  <Title>When Something Is Missing: Ellipsis, Coordination and the Chart</Title>
  <Section position="4" start_page="184" end_page="184" type="concl">
    <SectionTitle>
4. Conclusions
</SectionTitle>
    <Paragraph position="0"> We have presented a solution for two phenomena of ill-formedness (that is, ellipsis and coordination), a solution that fits coherently into a chart-based approach.</Paragraph>
    <Paragraph position="1"> As for intersentential ellipsis, it has been shown that no changes are needed for either the grammar or the basic parser: the algorithm requires only a resettlement of the chart (that is, the working memory) and the introduction of a new selecting function. Evidently, this is a great advantage in terms of clarity and modularity that is combined with the efficiency of the entire approach.</Paragraph>
    <Paragraph position="2"> For coordination it has been shown how changes that are brought to the apparatus are modularized so as not to fall into the intractability of other approaches. Both the algorithms have been implemented as enhancements of the WEDNESDAY 2 parser. The parser is used in the ALFresco interactive system, a multimodal dialogue prototype for the exploration of art history. 2 The examples in this paper refer to that prototype. Note, however, that the solutions proposed for ill-formed input in this paper are generally valid for other chart-based approaches.</Paragraph>
    <Paragraph position="3">  system has been developed in InterLisp and CommonLisp on Xerox 1186 and Sun4.</Paragraph>
  </Section>
class="xml-element"></Paper>