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<Paper uid="J89-4003">
  <Title>A FORMAL MODEL FOR CONTEXT-FREE LANGUAGES AUGMENTED WITH REDUPLICATION</Title>
  <Section position="10" start_page="0" end_page="0" type="concl">
    <SectionTitle>
9 SUMMARY
</SectionTitle>
    <Paragraph position="0"> We have seen that the RPDA model is very similar to the PDA characterization of context-free languages.</Paragraph>
    <Paragraph position="1"> Thus from an automata theoretic point of view, RPDA languages are very much like context-free languages.</Paragraph>
    <Paragraph position="2"> We have seen that both classes have similar closure properties, and so they are similar from an algebraic point of view as well. Moreover, the context-free languages and the RPDA languages have similar pumping lemmas that exclude many of the same unnatural language sets and even exclude them for the same reasons.</Paragraph>
    <Paragraph position="3"> Hence, the class of RPDAs are only mildly stronger than context-free grammars. However, the model is sufficiently strong to handle the many reduplication constructions that are found in natural language and that seem to place natural language outside of the class of context-free languages. The RPDA languages do not, as yet, have a grammar characterization similar to that of context-free grammar, but the RCFG grammars are context-free like grammars that do capture at least a large subclass of the RPDA languages.</Paragraph>
  </Section>
class="xml-element"></Paper>