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<Paper uid="C96-2101">
  <Title>Goal Formulation based on Communicative Principles</Title>
  <Section position="2" start_page="0" end_page="598" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Two general approaches can be distinguished in dialogue management: the structural approach, which uses a dialogue grammar to capture regularities of the dialogue in terms of exchanges and moves (Bilange, 1992; Cawsey, 1993; Grosz and Sidner, 1986), and the intention-based approach, which classifies the speaker's beliefs and intentions into speech acts, and uses planning operators to describe them (Appel% 1985; Allen and Perrault, 1980; Bunt et al., 1984). Both regard natural language as purposeful behaviour, but differ in how this behaviour is to be described. The former sees dialogues as products and compiles participants' beliefs and intentions into a predefined dialogue structure, whereas the latter focusses on the participants' goals, and hides the structure in the relations between acts which contain appropriately chosen sets of beliefs and intentions as their pre-conditions and effects.</Paragraph>
    <Paragraph position="1"> We will not go into detailed evaluation of the approaches, see e.g. (Jokinen, 1994), but draw attention to three aspects of dialogues which have *I am grateful to Yuji Matsumoto for providing an excellent resem'ch environment during my JSPS Postdoctoral Fellowship, and Graham Wilcock for helpful discussions.</Paragraph>
    <Paragraph position="2"> not been properly addressed before, although widely acknowledged in literature, and important in building robust Natural Language interfaces: 1. dialogue is a collaborative process and its structure is recognised by external observation, not prescribed as an internal constraint of dialogue management (Sacks et al., 1974; Clark and Wilkes-Gibbs, 1990), 2. the speakers' beliefs and intentions in a given dialogue situation are various, and cannot all be checked when deciding oil the next response (Cherniak, 1986), 3. communicative acts are part of social activity, constrained by normative obligations of rational agency (Allwood, 1976).</Paragraph>
    <Paragraph position="3"> We discuss these aspects from the point of view of cooperative goal formulation and present the Constructive Dialogue Model as a new approach to plan system responses. Our departure point is in general conmmnicative principles which constrain cooperative and coherent communication, and radical steps are taken in two respects: the dialogue grammar is abandoned as an infeasible way to describe dialogues, and also speech act recognition is abandoned as a redundant labelling of intention configurations. The first step means that the structure is not built according to structuring rules, but emerges from local coherence as the dialogue goes on. The second step means that beliefs and intentions are dealt with by reasoning about the utterance context and communicative constraints instead of speech act types. The decision about what to say next falls out as a result of the agent complying with the communicative principles which refer to the agent's rationality, sire cerity, motivation and consideration. Combined with contextual knowledge, they account for the acceptability of different alternative responses.</Paragraph>
    <Paragraph position="4"> The paper is organised as follows. The theoretical framework and its formalisation as the Constructive Dialogue Model are discussed in Section 2. Section 3 presents how the system's communicative goal is determined, and Section 4 provides comparision with related work. Finally, conclusions and filture directions are given in Section 5.</Paragraph>
  </Section>
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