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<Paper uid="P84-1065">
  <Title>Using Focus to Generate Complex and Simple Sentences</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1. Introduction
</SectionTitle>
    <Paragraph position="0"> Two problems in natural language generation are deciding what to say and how to say it. This paper addresses issues in the second of these tasks, that of surface generation. Given a semantic representation of what to say, a surface generator must construct an appropriate surface structure taking into consideration a wide variety of alternatives. When a generator is used to produce text and not just single sentences, one decision it must make is whether to use a sequence of simple sentences or a single complex one. We show how focus of attention can be used as the basis on which this decision can be made.</Paragraph>
    <Paragraph position="1"> A second goal of this paper is to introduce a formalism for surface generation that uses aspects of Kay's functional grammar (Kay, 1979) within a Prolog definite clause grammar (Pereira and Warren, 1980). This formalism was used to implement a surface generator that makes choices about sentence complexity based on shifts in focus of attention. The implementation was done as part of an explanation facility for a student advisor expert system being developed at Columbia University.</Paragraph>
  </Section>
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