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<Paper uid="E85-1006">
  <Title>NP PRP I ABOUT QOET I WHICH N/ ADJP N OGR AOJ TOPIC I I VERY IhlPORTANT /+WH NP VP t ~ N AUX V PP3 I I I 1 JOHN /PERF TALK * PP /,'/~ PRP NP I I</Title>
  <Section position="2" start_page="0" end_page="41" type="intro">
    <SectionTitle>
1 Overview
</SectionTitle>
    <Paragraph position="0"/>
    <Section position="1" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
1.1 The Grammar
</SectionTitle>
      <Paragraph position="0"> The ATN-Language used is - except for some minor deviations which are not of importance here in accordance with the one specified in \[BATES 78\] and covers the following subset of English:  - the most frequent verb types for declarative and imperative sentences and questions - direct and indirect WH-questions (for NPs, PPs, ADJPs, ADVPs) - direct and indirect Y/N-questions - sentential complements for verbs  and nouns various types of relative clauses (complete, reduced...) infintive construction (including control verbs with subject and nonsubject control) conjunction of complete constituents of every syntactic category subordinate clauses The grammar is written in very compact way, making extensively use of merging techniques; it comprises about 75 states and 170 arcs. The structure built by the grnmmar is cLui.te similar to the phrase structure trees usea m transformational gr, mmar on the S-structure level. (See appendix for some examplesD Structures of that type seem to us very suited for further semantic interpretation, since they offer a level of syntactic structure which both expresses ~'~mmatical functions (which are defined ~onfigurationally) and constituent structure features which axe important for certain aspects of logical form as e.g. quantifier scoping. Especially the use of the device of traces (as a phonologically empty phrase) allows for displaced elements to appear in the phrase marker in their surface postion and at the same time expresses the role which this element's original position plays in the corresponding predicate-argument structure.</Paragraph>
    </Section>
    <Section position="2" start_page="0" end_page="41" type="sub_section">
      <SectionTitle>
1.2 The Parser
</SectionTitle>
      <Paragraph position="0"> The parser itself is an active chart parser as described in \[KAPLAN 73\] and \[KAY 73\]; a detailed desciption of our implementation can be found in \[ENDERS et al 82\].</Paragraph>
      <Paragraph position="1"> By combining an active chart, which represents all fully analyzed (sub)constituents (the passive edges) and all incomplete partial derivations (the active edges) with an agenda, which contains an explicit representation of all further tasks to be processed, the chart parsing framework is especially suited for mul-ti-way analyses on syntacticly and lexically highly ambiguous input.</Paragraph>
      <Paragraph position="2"> Furthermore it offers a high degree of flexibility in the use of various control-structures beyond the uniform ones like depth-first and breadth-first. This can be achieved by means of heuristic measures of various types which are used for the weighting of the single tasks, thus being responsible for the ordering of the agenda. Thereby several features of the parser such as closure and attachment features and preference of certain readings not induced by attachment ambiguities can be varied effectively by simply modifying this weigthing function.</Paragraph>
      <Paragraph position="3"> There exist three versions of the parser differing in the strategy by which the grammar is processed:  - a mixed bottom-up/top-down version The latter two versions which both demand some pre-rocessing of the grammar are clearly better in terms of performance than the pure top-down version. They have about 75% of the memory requirements and need 80% of the cpu-time of the top-down version.</Paragraph>
      <Paragraph position="4"> All three versions have been implemented in Siemens-Interlisp running on Siemens mainframes. An implementation on a lisp machine is on the way.</Paragraph>
    </Section>
  </Section>
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