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<Paper uid="C94-1056">
  <Title>ABSTRACT GENERATION BASED ON RHETORICAL STRUCTURE EXTRACTION</Title>
  <Section position="4" start_page="344" end_page="345" type="metho">
    <SectionTitle>
3 RHETORICAl, STRUCTURE
</SectionTitle>
    <Paragraph position="0"> Rhetorical structure represents relations between varions chunks of sentences in the body of each section.</Paragraph>
    <Paragraph position="1"> In this paper, the rhetorical structure is represented by two layers: intra-paragraph and inter-paragral)h structures. An intra-paragraph structure is a structure whose representation units are sentences, and an inter-paragraph structure is a structure whose representation units are paragraphs.</Paragraph>
    <Paragraph position="2"> In text, various rhetorical patterns art,. used to clarify the principle of argument. Among them, co,&gt; nectivc expressions, which state inter-sentence relationships, are the most significant. The tyl)ieal grantmatical categories of the connective expressions are connectives and sentence predicates. They can I&gt;c divided into the thirty four categories which are exernplified in Table 1.</Paragraph>
    <Paragraph position="3">  kore wa (this is) tsumari (that is to say) k'okode wa ... wo nobeT~l (here ... is described)  The rhetorical relation of a sentence, which is the relationship to the preceding part of the text., can be extracted in accordance with the connective expression in the sentence. For a sentence without any explicit connective exl)ressions , extension relation is set to the sentence. The relations exemplitied in Table 1 are used for representing the rhetorical structure.</Paragraph>
    <Paragraph position="4"> Fig. 1 shows a paragral)h from an article titled &amp;quot;A Zero-Crossing l{ate Which Estimates the Frequency of a Speech Signal,&amp;quot; where underlined words indicate connective exl)ressions. Although the fourth and fifth sentences are clearly the exemplification of the first three sentences, the sixth is not. Also the sixth sentence is the concluding sentence for the first five. Thus, tile rhetorical structure for this text can be represented by a binary-tree as shown in Fig. 2.This structure is also represented as follows:  \[\[\[1 &lt;EZ&gt; 2\] &lt;gs&gt; \[3 &lt;E(\]&gt; \[4 &lt;EX&gt; 5\]\]\] &lt;sa&gt; 6\] 1: In tile context of discrete-time signals, zerocrossing is said to occur if successive samples have dilfereut algebraic signs.</Paragraph>
    <Paragraph position="5"> 2: Tile rate at which zero crossings occur is a simple measure of tile frequency content of st sig,ml.</Paragraph>
    <Paragraph position="6"> 3: This is .particularly true of narrow band signals.</Paragraph>
    <Paragraph position="7"> 4: For example, a si,msoidal signal of frequency P0, sanll)led at a rate fs, h,'~s i'~/t&amp;quot;~ samples per cycle of the siue wave.</Paragraph>
    <Paragraph position="8"> 5: Each cycle has two zero crossings so that the hmg-term average rate of zero-crossings is z = 2F0/s;;.</Paragraph>
    <Paragraph position="9"> 6: Thus, tile average zero-crossing rate gives a reasonable way to estinmte the frequency of a sine wave.</Paragraph>
    <Paragraph position="10">  The rhetorical structure is represented by a binary tree on the analogy of a syntactic tree of a natural language sentence. Each sub tree of the rhetorical structure forms an arg,rnentative constituent, just as each sub-tree of tile syntactic tree forms a gram,natical constituent. Also, a sub-tree of the rhetorical structure is sub-categorlzed by a relation of its parent node as well as a syntactic tree.</Paragraph>
  </Section>
  <Section position="5" start_page="345" end_page="345" type="metho">
    <SectionTitle>
5 Implementation Note
</SectionTitle>
    <Paragraph position="0"> The current version of TECIIDOC is running on Sun Spare stations with LUCI\]) CommonLISP 1.4 and LOOM 1.41 (a port to LOOM 2.1 is underway), and a PEN-MAN version fl'om 199i. The user interface is based on the CommonbISP Motif interface package CI,M and the application building tool GINA \[Spenke ct al., 1992\].</Paragraph>
  </Section>
  <Section position="6" start_page="345" end_page="345" type="metho">
    <SectionTitle>
Acknowledgements
</SectionTitle>
    <Paragraph position="0"> ~l'he success of the TECIIDOC i)rojeet depended heavily on eontril)utimls from a lltllllb(!r of student interns, in alphabetie;d order: Brigit.te Grote,, Sitll(Ira Kiibler, Itaihua Pan, .lochen Schoepl&gt;, Alex~mdot Sigel, Ralf Wagner, and Uta We, is. ~i'hey ~dl have contributed to gl'&amp;lltll'Lar or lexicon coverage ill one wa~y or another. Qerhard Peter has implemented TI'~CtlDOC-I, an intera(:tiw~ version giving c~tr mMntainanee ~tssist;tnce. Thorsten Liebig hats imph~mented TECtlDOC's user interface for workstatim~s using CLM and GINA, Ilartmut Peuehtmiiller has ~t(tded multimedia facilities ~md mouse-sensitive text mltlmt. We also have to thank the PlgNMAN ~tn(l LOOM groups ~tt USC/ISI and the KOMET project ~tt GMD Darmstadt, wire gave us inwdmd~te help.</Paragraph>
  </Section>
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