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<Paper uid="C92-2105">
  <Title>Self-Monitoring with Reversible Grammars</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> In many situations of communication a speaker need not to worry about the possible ambiguity of what she is saying because she can assume that the \]tearer will be able to disambiguate tile utter ance by means of contextual information or would otherwise ask for clarification. But in some situations it is necessary to avoid the risk of generating ambiguous utterances that could lead to misunderstanding by the hearer, e.g., during the proecss of writing text, where no interaction is possible, or when utterances refer to actions that have to bc performed directly or in some specific dialog situations (e.g. having an interview with a company).</Paragraph>
    <Paragraph position="1"> The need to generate un-ambiguous utterances is also relevant for the development of natural language generation systems. For example in the case of an intelligent help-system that supports the use of an operating system (Wilensky et al., 1984), asking an inexperienced user to 'f~emove the folder with the system tools' could \]lave tremendous effects on the system itself.</Paragraph>
    <Paragraph position="2"> If one assumes a modular division of the natural language generation task between two stages of the language production process -- deciding what to say (conecplual level) and deciding how to say it (grammatical level) -- it is not realistic to expect that the conceptual component will be able to specify the input for the grammatical component such that ambiguous utterances can be avoided.</Paragraph>
    <Paragraph position="3"> If it were possible to specify the input in such a way, then this would mean that the conceptual component has to provide all information needed by the grammatical component to make decisions about lexieal and syntactic choices. Hence, the conceptual component would need detailed information about the language to use. But this would blur the distinction between the grammatical and the conceptual level, because this would imply that both components share the grammar (see also Appelt (1989), Meteer (1990), Neumann (1991)). 1 In order to maintain a modular design additional mechanisms are necessary to perform some monitoring of the generator's output. Several authors argue for such additional mechanisms (Jameson and Wahlster, 1982; De Smedt and Kempen, 1987; Joshi, 1987; Levelt, 1989). For example, Levelt (1989) pointed out tbat &amp;quot;speakers monitor what they are saying and how they are saying it&amp;quot;. In particular he shows that a speaker is also able to note that what she is saying involves a potential ambiguity for the hearer and can handle this problem by means of selfmonitoring. null In this paper we describe an approach for self-monitoring which allows to generate un-ambiguous utterances in such situations where possible misunderstandings by tire user have to be avoided. The proposed method is based on a very strict integration of parsing and generation. During self-monitoring a generated ambigu 1As pointed out in Fodor (1983) one of tim chtaxacteristic properties of a module is that it is computationally autonomous. But a relevant coimideration of cornputationally autonomy is that nmdules do not share sourccs (in our case the grarmnar).</Paragraph>
    <Paragraph position="4"> AcrEs DE COLING-92, NANTES. 23-28 AOL'r 1992 7 0 0 PROC. OF COLING-92. NANTES, AUG. 23-28. 1992 ous utterance is parsed and the obtained alternative derivation trees are use.d ms a 'guide' for the 'monitored' generation step. We will show that such an integrated approach makes only sense with reversible grammars. To our knowledge, there is at present no algorithm that solves the problem of generating un-ambiguous utterances by nmans of self-monitoring.</Paragraph>
  </Section>
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