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<Paper uid="P99-1006">
  <Title>Discourse Relations: A Structural and Presuppositional Account Using Lexicalised TAG*</Title>
  <Section position="5" start_page="46" end_page="46" type="concl">
    <SectionTitle>
5 Conclusion
</SectionTitle>
    <Paragraph position="0"> In this paper, we have shown that discourse structure need not bear the full burden of discourse semantics: Part of it can be borne by other means.</Paragraph>
    <Paragraph position="1"> This keeps discourse structure simple and able to support a straight-forward compositional semantics.</Paragraph>
    <Paragraph position="2"> Specifically, we have argued that the notion of anaphoric presupposition that was introduced by van der Sandt (1992) to explain the interpretation of various definite noun phrases could also be seen as underlying the semantics of various discourse connectives. Since these presuppositions are licensed by eventualities taken to be shared knowledge, a good source of which is the interpretation of the discourse so far, anaphoric presupposition can be seen as carrying some of the burden of discourse connectivity and discourse semantics in a way that avoids crossing dependencies.</Paragraph>
    <Paragraph position="3"> There is, potentially, another benefit to factoring the sources of discourse semantics in this way: while cross-linguistically, inference and anaphoric presupposition are likely to behave similarly, structure (as in syntax) is likely to be more language specific. Thus a factored approach has a better chance of providing a cross-linguistic account of discourse than one that relies on a single premise.</Paragraph>
    <Paragraph position="4"> Clearly, more remains to be done. First, the approach demands a precise semantics for connectives, as in the work of Grote (1998), Grote et al. (1997), Jayez and Rossari (1998) and Lagerwerf (1998).</Paragraph>
    <Paragraph position="5"> Secondly, the approach demands an understanding of the attentional characteristics of presuppositions. In particular, preliminary study seems to suggest that p-bearing elements differ in what source can license them, where this source can be located, and what can act as distractors for this source. In fact, these differences seem to resemble the range of differences in the information status (Prince, 1981; Prince, 1992) or familiarity (Gundel et al., 1993) of referential NPs. Consider, for example: (11 ) I got in my old Volvo and set off to drive crosscountry and see as many different mountain ranges as possible. When I got to Arkansas, for example, I stopped in the Ozarks, although I had to borrow another car to see them because Volvos handle badly on steep grades.</Paragraph>
    <Paragraph position="6"> Here, the definite NP-like presupposition of the &amp;quot;when&amp;quot; clause (that getting to Arkansas is shared knowledge) is licensed by driving cross-country; the presupposition of &amp;quot;for example&amp;quot; (that stopping in the Ozarks exemplifies some shared generalisation) is licensed by seeing many mountain ranges, and the presupposition of &amp;quot;another&amp;quot; (that an alternative car to this one is shared knowledge) is licensed by my Volvo. This suggests a corpus annotation effort for anaphoric presuppositions, similar to ones already in progress on co-reference.</Paragraph>
    <Paragraph position="7"> Finally, we should show that the approach has practical benefit for NL understanding and/or generation. But the work to date surely shows the benefit of an approach that narrows the gap between discourse syntax and semantics and that of the clause.</Paragraph>
  </Section>
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