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<Paper uid="C04-1044">
  <Title>Polarization and abstraction of grammatical formalisms as methods for lexical disambiguation</Title>
  <Section position="9" start_page="0" end_page="0" type="concl">
    <SectionTitle>
LG LTAG
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    <Paragraph position="0"> ms perf. ms perf.</Paragraph>
    <Paragraph position="1">  prove performance or execution time with speci c methods for each formalism which are less abstract than destr.</Paragraph>
    <Paragraph position="2"> 6.2.1 Tailor-made abstraction for LG For the formalism LG, instead of complete destructuring, we keep some partial structural information to the polarized label. As the formalism is projective, we record some constraints about the continuous segment associated with a polarity. In this way, some neutralizations possible in the destr abstraction are not possible anymore if the two polarities have incompatible constraints (i.e. lie in di erent segments). This new morphism is called proj. The execution time is problematic but it might be controlled with a bound on the number of polarities in every multiset5 (see Figure 6)  Without bound for sentence (c), the running time is over 1 min.</Paragraph>
    <Paragraph position="3"> 6.2.2 Tailor-made abstraction for LTAG For LTAG: a possible weaker abstraction (called ltag) consists in keeping, with each polarity, some information of the LTAG tree it comes from. Rather than bags where all polarized labels are brought together, we have four kind of polarized pieces: (1) a positive label coming from the root of an initial tree, (2) a negative label coming from a substitution node, (3) a couple of dual label coming from the root and the foot of an auxiliary tree or (4) a couple of dual label coming from the two parts of a quasinode. Rules in this formalism re ect the two operations of LTAG; they do not mix polarities relative to adjunction with polarities relative to substitution. Figure 7 shows that the execution time is improved (wrt. Figure 5).</Paragraph>
    <Paragraph position="4"> Conclusion The examples we have presented above should not be used for a de nitive evaluation of particular methods, but more as a presentation of the exibility of our program: polarizing grammatical formalisms for abstracting them and parsing 5This bound expresses the maximum number of syntactic dependencies between a constituent and the others in a sentence.</Paragraph>
    <Paragraph position="5">  in the resulting abstract frameworks for disambiguating lexical selections. We have presented one general tool (the destructuring abstraction) that may apply to various grammatical framework. But we think that abstractions should be considered for speci c frameworks to be really e cient. One of our purpose is now to try the various tools we have developped to some large covering lexicons.</Paragraph>
    <Paragraph position="6"> So far, we have not taken into account the traditional techniques based on probabilities. Our point is that these should be seen as an other way of abstracting grammars. Our hope is that our program is a good way to mix di erent methods, probabilistic or exact.</Paragraph>
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