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<Paper uid="W06-1307">
  <Title>DRT Representation of Degrees of Belief</Title>
  <Section position="7" start_page="49" end_page="51" type="evalu">
    <SectionTitle>
5 Beliefs and Dialogue Acts
</SectionTitle>
    <Paragraph position="0"> When someone makes an assertion, they communicate not only information they assume to be new to the hearer, but also communicate to the hearer information about their own beliefs. In order to  model beliefs in dialogue, it is necessary to understand what the representation of dialogue involves. A dialogue is 'a cooperative undertaking of agents engaged in developing and transforming their common situation', involving verbal and non-verbal action (Heydrich et al. 1998: 21). In a dialogue, utterances give rise to dialogue acts (cf. agents' intention DRSs in Figures 1, 2 and 3), named speech acts by some, and conversation acts by others (Traum 1994).</Paragraph>
    <Paragraph position="1"> One of the features of dialogue acts is how they affect the agents' mental states. As Traum points out, '... speech acts are a good link between the mental states of agents and purposeful communication' (Traum 1999: 30). Each agent in dialogue needs to have a representation of their beliefs and the other agent's beliefs or cognitive state in order for a dialogue act to be felicitous in Austin's and Searle's sense (Asher 1986). That is to say, dialogue acts depend on agents' beliefs for interpretation. null  Each assertion made has one 'function' or more.</Paragraph>
    <Paragraph position="2"> For example, the function of a statement could be to make a claim about the world. Traum (1997) divides statements into 'assert', 're-assert', and 'inform'. 'Assert' is trying to 'change' the belief of the addressee. The result of assert is that the hearer now assumes that the speaker is trying to get the hearer to believe the assertion. 'Re-assert' can be used when participants try to verify old information, and not necessarily inform of something new. 'Inform' means that the speaker is trying to provide the hearer with information that the hearer did not have before. However, Traum does not go further to discuss cases where agents believe their utterances (Traum 1994: 14). It is one of the claims of this paper that agents in dialogue either strongly or weakly believe their utterances in order to be cooperative. It is possible to extend this approach in order to include cases where agents are purposefully deceitful. However, this is left for future research.</Paragraph>
    <Paragraph position="3"> The adapted dialogue acts, or functions, in thiss paper's treatment of beliefs in DRT are mainly 'inform', 'change belief' and 'other'. 'Inform' is used to communicate new information to the hearer, whereas 'change belief' (or to use Poesio and Traum's (1997b) dialogue act term 'assert') is used to change the hearer's beliefs about some proposition. The importance of the representation introduced in section 3 in relation to dialogue acts transpires in allowing us to make the distinction between the dialogue acts 'inform' and 'change belief' ('assert'). To 'inform' the hearer of X, the speaker needs to have the belief in her beliefs that the hearer does not believe X, i.e. bel(S,! bel(H, X)). This is a constraint to making an informative utterance. Figure 4 shows the speaker's beliefs before making the utterance in example (8).</Paragraph>
    <Paragraph position="4"> (8) The X-Files DVD is on sale on Amazon.</Paragraph>
    <Paragraph position="5"> The speaker believes the hearer does not already believe that the X-Files DVD is on sale on Amazon, drs3. This is demonstrated by the missing propositions representing 'on sale on Amazon' 'onSale(x, b4)' and 'at(a)' from drs3 in Figure 4.</Paragraph>
    <Paragraph position="6"> On the other hand, to make a 'change belief' or an 'assert', the speaker would have reason to believe that the hearer believes something different or the opposite of what the speaker believes, bel(S, bel(H, ! X)). The DRT treatment of beliefs proposed in this paper allows us to reflect this in  hearer believes the X-Files DVD is not on sale, 'not(onSale(x))'.</Paragraph>
    <Paragraph position="7"> The category 'Other' embraces any dialogue act other than 'inform' and 'change belief', whose recognition involves the same process explained for others, e.g. 'suggest', 'clarify', and 'explain'.4 The dialogue acts 'accept' and 'reject' come under the umbrella of feedback as they can be in response to, for instance, a 'suggest' dialogue act. The dialogue act 'clarify' is used when a hearer is having difficulty recognizing the speaker's utterance.5 On the other hand, 'explain' is when the speaker responds to the hearer's clarification request and provides a clarifying utterance. The hearer can accept, believe, or reject that explanation. The dialogue act 'suggest' also instigates one of three reactions: the hearer can accept, believe or reject that suggestion and may provide feedback to indicate which is his reaction. It is of more interest to this paper to examine the effects of dialogue acts on the hearer's beliefs, and what dialogue acts suggest about the speaker's beliefs.</Paragraph>
    <Section position="1" start_page="51" end_page="51" type="sub_section">
      <SectionTitle>
5.1 Feedback and Agents' Beliefs
</SectionTitle>
      <Paragraph position="0"> Traum (1994) suggests that when an assertion is made, the hearer has an obligation to produce an 'understanding act'. In general, acknowledgement is expected in Traum's treatment of speech acts. This means that when a hearer responds with 'okay', the hearer can be taken to be providing an acknowledgement and an acceptance. However, the hearer does not always provide feedback.</Paragraph>
      <Paragraph position="1"> Grounding often happens as a result of implicit rather than overt feedback and acknowledgement (Bunt 1995).6 In fact, the treatment outlined in this paper maintains that the lack of feedback is to be considered a form of 'weak positive feedback', an extension to Dynamic Interpretation Theory's (DIT) positive feedback (Bunt 1995). The hearer does not object to the speaker's utterance by not providing feedback, since if the hearer did object, he would explicitly do so.</Paragraph>
      <Paragraph position="2"> When the speaker makes an assertion, the hearer may indicate that the message has been received (weak positive feedback), example (9.b).</Paragraph>
      <Paragraph position="3"> Weak positive feedback may indicate understanding, continued attention, or acknowledgement, such as 'uh huh', and 'yeah' (Clark and Schaefer 1989). Another case of weak positive feedback is provided by example (9.a) where the hearer does not say anything. It is assumed that the hearer did not have any problems and has received the assertion, A. In the case of weak feedback, it can be argued that this represents the 'acceptance' of A.7 Another response for the hearer is 'strong posi- null as politeness, the hearer does not necessarily agree with the speaker, but does not wish to indicate it. The speaker can wrongly or rightly come to the conclusion that the hearer accepts the assertion.</Paragraph>
      <Paragraph position="4"> tive feedback' (another extension to DIT's positive feedback), where the hearer not only indicates reception of A, but also that she agrees that A (cf.</Paragraph>
      <Paragraph position="5"> drs7 Figure 3). This is where confirming adoption of new beliefs takes place, example (9.c). Rejecting A is another way of giving feedback, negative feedback, as in example (9.d).</Paragraph>
      <Paragraph position="6">  (9) Speaker: Mary loves John.</Paragraph>
      <Paragraph position="7"> a. Hearer: b. Hearer: aha.</Paragraph>
      <Paragraph position="8"> c. Hearer: I couldn't agree more! d. Hearer: No, Mary is besotted with  Tom! There are also degrees of belief that can be expressed according to the speech act used, firm versus 'tentative'. Poesio and Traum pay less attention to 'the attitudes expressed by the acts' (Poesio and Traum 1998: 221). Unlike Traum's model, the effects of the dialogue acts' employed in agents' DRSs on agents' beliefs are considered in this paper. Figure 6 demonstrates the link between feed-back dialogue acts and agents' beliefs.</Paragraph>
    </Section>
  </Section>
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