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<Paper uid="C82-1012">
  <Title>TREE DIRECTED GRAMMARS</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> Within the natural language information system PLIDIS \[6\] a semantic processor was implemented for the translation of syntactically analyzed sentences into expressions of a predicate calculus-orlented internal representation language. This semantic processor was designed according to a translation grammar defined by Wulz \[8\], which is similar to the transformation grammar introduced by Chomsky \[3\].</Paragraph>
    <Paragraph position="1"> The operations on trees which are defined in thetransformation grammar, i.e. deletion, insertion, and transposition of subtrees, are also available in the Wulz grammar. Therefore it can be assumed that it is equivalent to the transformation grammar with regard to the input/output-relation.</Paragraph>
    <Paragraph position="2"> But when the Wulz grammar was realized within PLiDIS for a section of German, only of a few of its possibilities was made use. No real transformation was prescribed by the PLIDIS translation rules, they only checked the parse tree and produced an output separated from this tree. Thus, what was realized in the PLIDIS translation rules can be better described by another kind of translation grammar, namely the tree directed grammar (TDG). When we investigate the TDGs and their relation to tree transducers it turns out that they are less powerful than transformation grammars.</Paragraph>
  </Section>
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