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<Paper uid="H91-1042">
  <Title>Statistical Agenda Parsing</Title>
  <Section position="8" start_page="223" end_page="223" type="concl">
    <SectionTitle>
DELPHI RESULTS
</SectionTitle>
    <Paragraph position="0"> Measurements of chart-size and time reductions for BBN's DELPHI grammar running on the ATIS training and test sets indicate the improvements possible with several variations of the basic agenda mechanism. For example, using the structured agenda on 551 sentences of training data from June 1990, the chart size was reduced by a factor of 3.24, and the total processing time reduced by a factor of 1.82.</Paragraph>
    <Paragraph position="1"> This result underestimates the improvement gained by agenda parsing, since somewhat more than 10% of the &amp;quot;sentences&amp;quot; in the training data were ill-formed according to our grammar (many were ill-formed according to any plausible grammar!). Since a properly operating agenda system will eventually produce the same chart that the GHR parser does, and since that entire chart must be searched before a string is determined to be unparseable, the performance of any agenda mechanism must reduce to that of the GHR parser for such inputs.</Paragraph>
    <Paragraph position="2"> Another set of experiments was performed with a set of 539 &amp;quot;parseable&amp;quot; strings taken from the combination of the June 1990 and February 1991 ATIS training set. For this set the speedup was a factor of 3.8 and the chart size reduction was well over 3.5. (The hedge on chart size reduction is because data for the chart size of 5 sentences in the GHR parser was not obtained, the charts overflowed available memory . At this time the ratio of that chart size to the size of the agenda parser chart was over 30.) The introduction of probabilistic agenda parsing, combined with the application of software engineering techniques, has sped up natural language analysis considerably. The average time for parsing, semantic interpretation and discourse processing (of a 551 sentence training corpus) in our DELPHI system was lowered to 1.43 seconds per sentence, with a median time of 0.99 seconds, on a Sun 4/280.</Paragraph>
  </Section>
class="xml-element"></Paper>