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<Paper uid="J83-1001">
  <Title>Paraphrasing Questions Using Given and New Information 1</Title>
  <Section position="4" start_page="0" end_page="0" type="intro">
    <SectionTitle>
4. Linguistic Background
</SectionTitle>
    <Paragraph position="0"> As mentioned earlier, the lexicon and the data base are the sole sources of world knowledge for CO-OP.</Paragraph>
    <Paragraph position="1"> While this design increases CO-OP's portability, it means that little semantic information is available for the paraphraser's use. Contextual information is also limited since no running history or context is maintained for a user session in the current version. The input the paraphraser received from the parser is a syntactic parse tree of the question. Using this information, the paraphraser must construct a question that differs in phrasing from the original. The following question must therefore be addressed: What reasons are there for choosing one syntactic form of expression over another? Some linguists maintain that word order is affected by functional roles elements play within the sentence. 3 Terminology used to describe the types of roles that can occur varies widely. Some of the distinctions that have been described include given/new, topic/comment, theme/rheme, and presupposition/focus. Definitions of these terms, however, are not consistent. 4 Nevertheless, one influence on expression does appear to be the interaction of sentence content and the beliefs of the speaker concerning the knowledge of the listener. Some elements in the sentence function in conveying information the speaker assumes is present in the &amp;quot;consciousness&amp;quot; of the listener (Chafe 1976). This information is said to be contextually dependent, either by virtue of its presence in the preceding discourse or because it is part of the shared world knowledge of the dialog participants. In a question-answering system, shared world-knowledge 3 Some other influences on syntactic expression are discussed in Morgan and Green 1973. They suggest that stylistic reasons, in addition to some of the functions discussed here, determine when different syntactic constructions are to be used. They point out, for example, that the passive tense is often used in academic prose to avoid identification of agent and to lend a scientific flavor to the text.</Paragraph>
  </Section>
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