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<Paper uid="C92-1054">
  <Title>Redundancy in Collaborative Dialogue</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
3 Inference of Understanding
</SectionTitle>
    <Paragraph position="0"> This section examines the assumption from the DETER-MINISTIC MODEL that: (2) Propositions representing beliefs and intentions get added to the context by the unilateral action of one conversant 3. This assumption will also be examined in section 5.</Paragraph>
    <Paragraph position="1"> The key claim of this section is that agents monitor the effects of their utterance actions and that the next action by the addressee is taken as evidence of the effect of the speaker's utterance 4. That the utterance will have the intended effect is only a hypothesis at the point where the utterance has just been made, irrespective of the intentions of the speaker. This distinguishes this account from others that assume either that utterance actions always succeed or that they succeed unless the addressee previously believed othecwise\[ll, 8\].</Paragraph>
    <Paragraph position="2"> I adopt the assumption that the participants in a dialogue are trying to achieve some purpose\[7\]. Some aspects of the structure of dialogue arises from the structure of these purposes and their relation to one another. The minimal purpose of any dialogue is that an utterance be understood, and this goal is a prerequisite to achieving other goals in dialogue, such as commitment to future action. Thus achieving mutual belief of understanding is an instance of the type of activity that agents must perform as they collaborate to achieve the purposes of the dialogue. I claim that a model of the achievement of mutual belief of understanding can he extended to the achievement of other goals in dialogue.</Paragraph>
    <Paragraph position="3"> Achieving understanding is not unproblematic, it is a process that must be managed, just as other goal achieving processes are\[3\]. Inference of mutual understanding relies upon some evidence, e.g. the utterance that is made, and a number of underlying assumptions.</Paragraph>
    <Paragraph position="4"> The assumptions are given with the inference rule below. null say(it, B, u, p) --A-&gt; aThis is an utterance action version of the STRIPS assumption. 4Except for circumstances where it is clear that the flow of the conversation has been interrupted.</Paragraph>
    <Paragraph position="6"> This schema means that when A says u to B intending to convey p, that this leads to the mutual belief that B understands u as p under certain assumptions. The assumptions are that A and B were cnpresent, that B was attending to the utterance event, that B heard the utterance, and that B believes that the utterance u realizes tim intended meaning p.</Paragraph>
    <Paragraph position="7"> The \[evidence-typeJ annotation indicates the strength of evidence supporting the assumption. All of the assumptions start out supported by no evidence; their evidence type is therefore hypothesis. It isn't until after the addressee's next action that an assumption can have its strength modified.</Paragraph>
    <Paragraph position="8"> The claim here is that one class of IRU's addresses these assumptions underlying the inference of mutual understanding. Each type of IRU, the assumption addressed and the evidence type provided is given in Figure 1. Examples are provided in sections 3.1 and 3.2. It is also possible that A inteuds that BY saying u, which realizes p, B should make a certain inference q.</Paragraph>
    <Paragraph position="9"> Then B's understanding of u should include B making this inference. This adds an additional assumption: bel(B, license (p, q)) \[evidence-typeJ Thus assuming that q was inferred relies on the assumption that B believes that p licenses q in the context. null Figure 1 says that prompts, repetitions, paraphrases and making inferences explicit all provide linguistic evidence of attention. All that prompts such as sh huh do is provide evidence of attention. However repetitions, paraphrases and making inferences explicit also demonstrate complete hearing. In addition, a para~ phrase and making an inference explicit provides linguistic evidence of what proposition the paraphraser believes the previous utterance realizes. Explicit inferences additionally provide evidence of what inferences tile inferrer believes the realized proposition licenses in this context.</Paragraph>
    <Paragraph position="10"> Ill each case, the IRU addresses one or more sumptions that have to be made in order to infer that mutual understanding has actually been achieved.</Paragraph>
    <Paragraph position="11"> The assumption, rather than being a hypothesi~ or a default, get upgraded to a support type of linguistic as a result of the IRU. The fact that different II~U's address different assumptions leads to the perception that some 1KU's are better evidence for understanding than others, e.g. a PARAPHRASE i8 stronger evidence of understanding than a REPEAT\[3\].</Paragraph>
    <Paragraph position="12"> In addition, any next utterance by the addressee can upgrade the strength of the underlying assumptions to default (See Figure 1). Of course default evidence is weaker than linguistic evidence. The basis for these default inthrences will be discussed in section 5.</Paragraph>
    <Section position="1" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
3.1 Example of a Repetition
</SectionTitle>
      <Paragraph position="0"> Consider example 1 ill section 1. Ray, in (8), repeats IIarry's assertion from (7). This upgrades the evidence for tile assumptions of hearing and attention associated with utterance (7) from hypothesis to Xinguistic.</Paragraph>
      <Paragraph position="1"> The assumption about what proposition p7 is realized by u7 remains a default. This instantiates the infer-ACRES DE COL1NG-92, NANTI~S, 23-28 Aotrr 1992 3 4 7 Paoc. OF COLING-92, NAIVrr~s, Auc;, 23-28. 1992 ence rule for understanding as follows: say(harry, ray, uT, pT) --I-&gt;</Paragraph>
      <Paragraph position="3"> Because of the WEAKEST LINK assumption, the belief about understanding is still a default.</Paragraph>
    </Section>
    <Section position="2" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
3.2 Example of a Paraphrase
</SectionTitle>
      <Paragraph position="0"> This assumption is challenged by a number of cases in naturally occurring dialogues where inferences that follow from what has been said are made explicit. I restrict the inferences that I discuss to those that are (a) based on information explicitly provided in the dialogue or, (b) licensed by applications of Gricean Maxims such as scalar implicature inferences\[9\].</Paragraph>
      <Paragraph position="1"> For example the logical omniscience assumption would mean that if l(a) and (b) below are in the context, then  (c) will be as well since it is entailed from (a) and (b). (1) a. You can buy an I It A if and only if you do NOT have an existing pension plan, b. You have an existing pension plan.</Paragraph>
      <Paragraph position="2"> c. You cannot buy an I It A, Consider the following excerpt: Exawple 2: (18) h. i see. are there any uther children beside your gila? (19) d. no (20) h. YOUR WIFE IS AN OILY CHILD (21) d. right, and uh wants to give her some security ..........</Paragraph>
      <Paragraph position="3">  Harry's utterance of (20) is said with a falling intonational contour and hence is unlikely to be a question. This utterance results in an instantiation of the inference rule as follows: say(harry, ray, u20, p20) --l-&gt;</Paragraph>
      <Paragraph position="5"> In this ease, the belief about understanding is supported by linguistic evidence since all of the supporting assumptions are supported by linguistic evidence. Thus a paraphrase provides excellent evidence that an agent actually understood what another agent meant.</Paragraph>
      <Paragraph position="6"> In addition, these IItU's leave a proposition salient, where otherwise the discourse might have moved on to other topics. This is part of the CENTERING function of IKU's and is left to future work.</Paragraph>
    </Section>
  </Section>
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