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<Paper uid="E93-1042">
  <Title>NEW FRONTIERS BEYOND CONTEXT-FREENESS: DI-GRAMMARS AND DI-AUTOMATA.</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
Abstract
</SectionTitle>
    <Paragraph position="0"> A new class of formal languages will be defined the Distributed Index Languages (DI-languages). The grammar-formalism generating the new class - the DI-grammars - cover unbound dependencies in a rather natural way. The place of DI-languages in the Chomsky-hierarchy will be determined: Like Aho's indexed Languages, DI-languages represent a proper subclass of Type 1 (contextsensitive languages) and properly include Type 2 (context-free languages), but the DI-class is neither a subclass nor a superclass of Aho's indexed class. It will be shown that, apart from DI-grammars, DI-languages can equivalently be characterized by a special type of automata - DI-automata. Finally, the time complexity of the recognition-problem for an interesting subclass of DI-Grammars will approximately be determined.</Paragraph>
  </Section>
class="xml-element"></Paper>