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<Paper uid="W97-0715">
  <Title>A Formal Model of Text Summarization Based on Condensation Operators of a Terminological Logic</Title>
  <Section position="2" start_page="0" end_page="97" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> From its very begmmng, the development of text understanding systems has been mhmately trod to the field of knowledge representahon and reasoning methods (Schank ~ Abelson 77) ThLs close relationship was justtfied by the observation that any adequate form of text understanding not only reqmres grammatical knowledge about the particular language, but also, among others, has to incorporate knowledge about the dommn the text deals with Thus, the referencing capabdltms of knowledge representation languages were conmdered crucial for any adequate design of text understanding systems Out of thLs tradlhon a series of knowledge-based text summarizahon systems evolved, the methodology of whlch was almost exclnslvely based on.</Paragraph>
    <Paragraph position="1"> the Schanklan-type of Conceptual Dependency (CD) representations (e g, (Culhngford 78, Lehnert 81, DeJong 82, Dyer. 83, Trot 85, Alterman 86)) CD representations, however, are formally underspeclfled representation devices lacking any serious formal foundatlon According to thin, the summanzahon operatlons these first-generatlon systems provide use only informal heurlshcs to determine the sahent top-Ics from the text representahon structures for the purpose of summanzatlon A second generahon of summarlzahon systems then adapted a more mature knowledge representahon approach, one based on the evolvlng methodolo~cM framework of hybrid, dasslficatlon-based knowledge representahon languages (cf (Woods &amp; Schmolze 92) for a survey) Among these systems count SUSY (Fum et al 85), SCISOR (Ran 87), and TOPIC (Rennet &amp; Hahn 88), but even m these frameworks no attempt was made to properly integrate the text summarlzahon processmto the formal reasomag mechanmms of the underlying knowledge representahon language Thin m where our interest comes in We propose here. a model of text summarlzatlon that m entirely embedded m the framework of a clasmficatlon-based model of termmologlcal reasoning Text summarlzahon m conmdered a formally gulded transformation process on knowledge representahon structures, the so-called text knowledge base, as derived by a natural language text parser The transformahons revolved inherit the formal rigor of the underly-Ing knowledge representatlon model, as correspondmg summarlzahon operators bmld on that model Thus, our work describes a methodologlcally coherent, representahon-theory-based approach to text summarlzahon that has been lacking m the hterature so far (for a survey cf (Hutchms 87)) Aside from these purely representahonal conslderahons, the terminological reasoning framework for the summanzatlon model we propose offers a variety of subtle parameters on whlch scalable summarization processes can be based Thin contrasts, m particular, wlth those approaches to text summanzahon whlch almost entlrely rely upon bmlt-m features of frame and scrlpt-based representatlons and, consequently,  provide rather mmpie reduction heunstxcs m order to produce text summarms (e g, (DeJong 82, Young Hayes 85)) The formal model we present has been tested m TOPIC (Re!met &amp; Hahn 88), a text summanzat~an system Which has been apphed to expos~tory texts m the domain of computer eqmpment as well as to various kinds of texts dealing with legal lssUes (company regulations, adwsory texts, etc ) This paper m organized as follows In Section 2 we lay down a description of the syntax and semantics of the terminological logic which serves as the formal backbone for the specification of condensation operators on (text) knowledge bases From thin formal descnptmn we then turn to the formal model of text summarization m Section 3</Paragraph>
  </Section>
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