<?xml version="1.0" standalone="yes"?>
<Paper uid="P86-1034">
  <Title>The Structure of User-Adviser Dialogues: Is there Method in their Madness? Raymonde Guindon Microeleetronies and Computer Technology Corporation - MCC</Title>
  <Section position="2" start_page="0" end_page="224" type="intro">
    <SectionTitle>
INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> The goal of this paper is to find evidence for the notion of dialogue structure as it has been developed in computational linguistics (Grosz, 1977; Sidner and Grosz, 1985). The role of two hypothesized determinants of discourse structure will be examined: i) the structure of the task that the user is trying to accomplish and the user's goals and plans arising from the task; 2) the strategies available to the user when the user is unable to achieve the task or parts of the task (i.e., meta-plans). The study of dialogue structures is important because computationally complex phenomena such as anaphora resolution have been theoretically linked to the task and dialogue structures.</Paragraph>
    <Paragraph position="1"> Dialogue Structure: A Key to Computing Focus Given the computational expense of searching, of inferential processing, and of semantic consistency checking required to resolve anaphors, restricting the search a priori to a likely set of antecedents seems advantageous. The a priori restriction on the set of potential antecedents for anaphora resolution has been called focusing (Grosz, 1977; Guindon, 1985; Reichman, 1981; Sidner, 1983). Grosz defines a focus space as that subset of the participant's total knowledge that is in the focus of attention and that is relevant to process a discourse segment.</Paragraph>
    <Paragraph position="2"> Task-oriented dialogues are dialogues between conversants whose goals are to accomplish some specific tasks by exchanging information through the dialogues. Task-oriented dialogues are believed to exhibit a structure corresponding to the structure of the task being performed. The entire dialogue is segmented into subordinated subdialogues in a manner parallel to the segmentation of the whole task into subordinated subtasks. Grosz (1977) assumes that the task hierarchy imposes a hierarchy on the subdialogue segments. As a subtask of the task is performed (and its corresponding subdialogue is expressed), the different objects and actions associated with this subtask come into focus. As this subtask is completed (and its corresponding subdialogue), its associated objects and actions leave focus. The task of which the completed subtask is a part then returns in focus. The segmentation of a dialogue into interrelated subdialogues is associated with shifts in focus occurring during the dialogue.</Paragraph>
    <Paragraph position="3"> Detailed task structures for each problem given in this study can be found in Guindon, Sladky, Brunner, and Conner (1986).</Paragraph>
    <Paragraph position="4"> A cognitive model of anaphora resolution and focusing is provided in Guindon (1985) and Kintsch and van Dijk (1978).</Paragraph>
    <Paragraph position="5"> Human memory is divided into a short-term memory and a long-term memory. Short-term memory is divided into a cache and a buffer. The cache contains items from previous sentences and the buffer holds the incoming sentence. Short-term memory can only contain a small number of text items and its retrieval time is fast. Long-term memory can contain a very large number of text items but its retrieval time is slow. During the integration of a new sentence, the T most important and R most recent items in short-term memory are held over in the cache. Items in focus are the items in the cache and are more rapidly retrieved. Items not in focus are items in long-term memory and are more slowly retrieved. Because the cache contains important items that are not necessarily recent, pronouns can be used to refer to items that have been mentioned many sentences back. An empirical study demonstrates the cognitive basis for focusing, topic shifts, the use of pronominal noun phrases to refer to antecedents in focus, and the use of non-pronominal noun phrases to refer to antecedents not in focus.</Paragraph>
    <Paragraph position="6">  Gross and Sidner (1985) distinguishes three structures in a discourse structure: 1) the structure of the sequence of utterances, 2) the structure of the intentions conveyed, and 3) the attentional state. Distinguishing these three structures gives a better account of discourse phenomena such as boundary markers, anaphors, and interruptions. This paper will cover mainly the second structure and will attempt to find evidence linking the dialogue structure to the task structure. The main point is that the structure of the intentions conveyed in the discourse should mirror to some extent the task structure (but see the next section). The first structure of the dialogue, the structure of the sequence of utterances, will actually be examined with the pronominal and non-pronominal noun phrase distributions, the antecedent distribution, and the boundary marker analyses. We expect that these three analyses will support the derived dialogue structure, the intentional structure. The last structure, the attentional structure, is not discussed here but has been discussed in Guindon (1985). ',\ The main point of &amp;quot;focusing&amp;quot; theories of anaphora resolution is that the discourse structure, based on the task structure, is a crucial determinant of which discourse entities are held in focus and are readily accessible for anaphora resolution. Subdialogues that are in focus are contexts that are used to restrict the search for antecedents of anaphors.</Paragraph>
    <Section position="1" start_page="224" end_page="224" type="sub_section">
      <SectionTitle>
Task Structure Can Only Partially Determine
Dialogue Structure
</SectionTitle>
      <Paragraph position="0"> In any case, the task structure can only partially determine the goals and plans of the novice user and, indirectly, the dialogue structure. This is because the novice user does not have a good model of the task and is in the process of building one and because the adviser only has a partially correct model of what the novice user knows about the task. The verbal interaction between the user and the adviser is not just one of execution of plans and recognition of plans but rather one of situated actions and detection and repair of imperfect understanding (Suchman, 1985).</Paragraph>
      <Paragraph position="1"> As a consequence, the dialogue structures from our data contained subdialogues that functioned as clarification (i.e., request of information) to correct imperfect understanding or as acknowledgement to verify understanding between the participants. The notion of meta-plans allows us to account for the presence of clarification and acknowledgement subdialogues (see Litman and Allen, 1984).</Paragraph>
    </Section>
  </Section>
class="xml-element"></Paper>