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<Paper uid="C90-3051">
  <Title>Incremental Parsing and Reason Maintenance</Title>
  <Section position="6" start_page="0" end_page="0" type="concl">
    <SectionTitle>
5 Conclusion
</SectionTitle>
    <Paragraph position="0"> This paper compares JTMS- and ATMS-based approaches to adopting reason-maintenance techniques in incremental parsing (arid interpretation). A major problem with the JTMS-based approach is that it is fundamentally limited to representing one context (one hypothesized interpretation). One consequence of this is that competing interpretations cannot be compared. Another consequence is that the system is constantly forced to commit rash choices and to spend a large part of its time revising these choices when faced with couflicging information. This situation appears even worse in light of the relative inefficiency of JTMSs. Zernik arm Brown (1988) in a sen,m take this approach to its extreme, using de~ fault reasoning and dependency-directed backtracking to guide the entire parsing and interpretation process. It is however not clear why one would want to confine oneself to a single hypothesi,; at each step of this process, lp&amp;quot; \[t is also not clear that default choices and dependency-directed backtracking is the best way to guide se~rch in natural-language analysis with respect to phenomena like syntactic alnbiguity.</Paragraph>
    <Paragraph position="1"> From a computational point of view, there are well-known and ell'icient teehniques, such as chart parsing, that work by developing syntactic alter,retires in parallel. Dora a psycholinguistic point of view, although the issue is under discussion, there are both theoretical arguments and empirical evidence supporting the claim thai, alternative interpretations are explored in parallel (Crain and Steedman 1985). Incidentally, one of the rationales for this c\]aim is that it is a prerequisite for eoml)eting interpretations l.o be compared.</Paragraph>
    <Paragraph position="2"> In contr~st to this, an ATMS solves or circumvents the major problems posed by a J'I'MS. The ATMS supports eificient development and coml)arison of all legal (possibly contradictory) analyses; an ATMS-style parser thus seems more in accordance with computational practice as well as with psycholinguistic evidence. Furthermore, the relationship between NI'MSs and chart parsing is in itself an advantage, because it facilitates cross-fertilization of the respective subtlelds. In particular, it might be possible to make use of recertt advances within reason maintenance in encoding defatflt reasoning for the purpose of handling certain I)roblems in semantic and pragnmtic interpretation. Ultimately, this might provide for a more unitbrm handling of syl&gt; tax, semantics, and l)ragmatics.</Paragraph>
    <Paragraph position="3"> 12Note that Zernik and Brown also do not make use of look-ahead or delayed processing to facilitate intelligent choices.</Paragraph>
  </Section>
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