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<Paper uid="C92-4174">
  <Title>DIRECT PARSING WITH METARUI~ES</Title>
  <Section position="9" start_page="0" end_page="0" type="concl">
    <SectionTitle>
7 Conclusion
</SectionTitle>
    <Paragraph position="0"> Metarules are an interesting device to express some important generalizations on phrase structure rules of a uatural language granlmar. If they are used in preprocessing to compile a huge set of rules out of a small set of basic ones, file parsing process may become very inefficient, because it has to care for the set of basic rules and additionally for the rules which have been derived from them and are very similar to the basic ones. When metarules are applied directly during the parsing process, only the set of basic rules in connection with the mctarules have to be considered by the parser. This reduces the set of intermediate ~fiutions (inactive edges) to be stored considerably.</Paragraph>
    <Paragraph position="1"> lu order to apply mEtarulcs directly, it has to be guaranteed that the given set of meturules will temlinate if all metarules fulfil the tcrraination criterion in section 4. We gavc tile termination proof for the metarules of our German grammar in secdon 5. We think that with file help of this criterion the termination of every relevant set of ioelarules can be proven, because a metarule is defined to change something in an ID rule, either to delete a category, to modify Sonic feature values, to add a category or to do a combination of all. With the termination criterion it is possible to construct a device which automatically proves the - termination of a given set of metarules. This algorithm computes the set of operator precedences from the feature values which are changed on the categories of a metarule.</Paragraph>
    <Paragraph position="2"> To enable the parser to process metarules like Uszkoreit's tor AdvPs in section 3, which add categories to basic ID rules and for which the termination can be proven, will be suhject to future work.</Paragraph>
  </Section>
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