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<Paper uid="W02-0212">
  <Title>Conditional Responses in Information-Seeking Dialogues</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
2 Uses of conditional responses
</SectionTitle>
    <Paragraph position="0"> In this section we present two different types of CRs and discuss in what contexts they are appropriate.</Paragraph>
    <Paragraph position="1"> CRs can be used as answers to yes/no-questions.3 A CR does not provide a yes/no answer simpliciter, though: It provides an answer that is contingent on the value of some attribute. Consider (1). The system's reply (1:S.1) provides an answer that is contingent on the value of the citizenship attribute. If the value is (or implies) EU citizenship, the answer is negative: If the user is an EU citizen, she does not need a visa to enter the U.S.</Paragraph>
    <Paragraph position="2"> The CR in (1) also seems to suggest the contrapositive that if the value is &amp;quot;non-EU-citizen&amp;quot;, the answer is positive. (2) illustrates the opposite case.</Paragraph>
    <Paragraph position="3"> We consider this additional suggestion an implicature. The assertions and implicatures that arise from 3Corpora show also occurrences of CRs in response to statements, cf. (Karagjosova and Kruijff-Korbayov'a, 2002). CRs are summarized in Figure 1.</Paragraph>
    <Paragraph position="4"> Green &amp; Carberry (1999) characterize CRs in terms of the speaker's motivation to provide information &amp;quot;about conditions that could affect the veracity of the response&amp;quot;. However, they only consider cases like (4) in which the A/V on which the CR is contingent has not yet been determined in the preceding context (or cannot be assumed). Cases like (5) where the A/V has been determined are left unnoticed.4 We discuss each of the cases below.</Paragraph>
    <Paragraph position="5"> Not-determined A/V. The A/V on which a CR is contingent can be one that has not yet been determined in the preceding context, as in (1) and (4).</Paragraph>
    <Paragraph position="6"> We call this type of CR a non-determined A/V CR (NDCR). Besides the assertion and the implicature that answer the yes/no question as specified in Figure 1, the NDCR amounts to indirectly giving rise to the question &amp;quot;whether c holds&amp;quot;.</Paragraph>
    <Paragraph position="7"> Consider the user's utterances in (6) as continuations of (1). They show that the implicitly raised question cannot be answered just by &amp;quot;yes&amp;quot; or &amp;quot;no&amp;quot;.  Rather, it requires some content that matches with c.</Paragraph>
    <Paragraph position="8"> (6) U.2: Yes.jNo.</Paragraph>
    <Paragraph position="9"> U.20: Yes, I am.jNo, I am not.</Paragraph>
    <Paragraph position="10"> U.200: Yes, I have German citizenship.j  No, I have Czech citizenship.</Paragraph>
    <Paragraph position="11"> The responses in (6:U.2) could be interpreted as acknowledgments, but certainly not as answers to whether the user is an EU citizen. This is corroborated by the following continuation of (6:U2') where the system does answer the pending question.</Paragraph>
    <Paragraph position="12"> (7) S.2: Then you do (not).</Paragraph>
    <Paragraph position="13"> S.20: Then you do (not) need a visa.</Paragraph>
    <Paragraph position="14"> (7:S.2) is elliptical for (7:S.20). Correct resolution of the ellipsis is possible only if the question whether the user needs a visa is the topmost QUD.</Paragraph>
    <Paragraph position="15"> The need to answer the implicitly raised question depends on what goals the participants try to achieve. &amp;quot;Do I need a visa?&amp;quot; in (1) is satisfactorily answered with either a yes or a no, or when enough information is provided so the asker can find out the answer herself. On the other hand, consider (8).</Paragraph>
    <Paragraph position="16">  In (8) the response is contingent on whether the user wants to fly economy class. Before flight selection can proceed further, the question whether c holds must be answered. In order to satisfy its goal of finding a flight which satisfies the user requirements, the system does need to know whether c holds to find out whether q holds. This is a difference between (8) and (1). In (1), the system's goal is merely to answer the user's question.</Paragraph>
    <Paragraph position="17"> To summarize, the interpretation of a CR in response to a question whether q in a context where c has not been established is that (i) it is still not determined whether q, because (ii) the answer (specified in Figure 1) is contingent on c, and thus (iii) the question whether c holds is implicitly raised.</Paragraph>
    <Paragraph position="18"> As for production, it is appropriate for the system to produce a NDCR when (i) answering a yes/noquestion whether q, where (ii) the answer is either q or not-q, depending on some additional A/V c which has not yet been established in the context. We conjecture that whether a positive or a negative CR is more cooperative in a particular context depends on what the preferred answer to the question &amp;quot;whether q&amp;quot; is assumed to be.</Paragraph>
    <Paragraph position="19"> Contextually-determined A/V. Another context in which a CR is appropriate is when an answer to a yes/no-question is contingent on an A/V that has already been established in the preceding context, as in (5). We call this type of CR a contextuallydetermined A/V CR (CDCR).</Paragraph>
    <Paragraph position="20"> What does a CDCR communicate besides the assertion and implicature that answer the question as specified in Figure 1? We suggested in x1 that it initiates a negotiation about the already established A/V. However, this cannot happen by simply raising the question whether c holds, because c has already been established. We suggest that a CDCR implicitly proposes to consider changing the A/V: It re-raises the question whether c holds. Re-raising c differs from raising a &amp;quot;new&amp;quot; question at least in two aspects: c must be negotiable, and re-raising c means it cannot be answered simply by providing a sufficiently discriminative positive or negative response. To see the difference, consider (5) with  (5:S.2) continued by the following utterances.</Paragraph>
    <Paragraph position="21"> (9) U.3: Yes.jNo.</Paragraph>
    <Paragraph position="22"> U.30: Yes, I do.jNo, I don't.</Paragraph>
    <Paragraph position="23"> U.300: Yes, I want business class.j No, I don't want business class.</Paragraph>
    <Paragraph position="24"> (10) U.3: OK, I can fly economy.</Paragraph>
    <Paragraph position="25"> U.30: But I do want business class.</Paragraph>
    <Paragraph position="26"> (11) U.3: How about Tuesday?  Like the responses in (6), the response in (9:U.3) cannot be interpreted as answers to whether the user wants to change her mind from business to economy class. It seems hard to interpret even as acknowledgment. But then we observe a number of differences from the NDCR in (6): The responses in (9:U.30) and (9:U.300) are not appropriate as answers to the implicitly re-raised c, because a revision of an A/V is involved. Hence, some kind of acknowledgment of the revision is needed in addition to answering whether or not the A/V is to be revised (and how). Such acknowledgments are present in (10). In (10:U.3), 'OK' can be seen as acknowledging the revision from business to economy class. In (10:U.30), 'but' acknowledges the contrast between the proposed revision and the actual preservation of the A/V (here, business class). The continuation in (11), on the other hand, refuses the proposed revision only implicitly by proposing instead to check the flight possibilities on another day.</Paragraph>
    <Paragraph position="27"> Another observation concerning a CDCR is that it cannot immediately follow after an utterance in which the value is established, as the inappropriateness of (12:S.1) and (12:S.10) shows.</Paragraph>
    <Paragraph position="28"> (12) U.1: Can I fly business class from K&amp;quot;oln to Paris on Sunday? S.1: Not if you want business class.</Paragraph>
    <Paragraph position="29"> S.10: Yes if you want economy class.</Paragraph>
    <Paragraph position="30"> Intuitively, the reason for this is that there needs to be some degree of uncertainty (in the sense of being assumed but not known to be shared) about the A/V. For example, in (5), the business class requirement is assumed to be maintained when the day is revised. The inappropriateness of (12:S.1) and (12:S.10) can also be explained on purely semantic grounds. When both the assertion and the implicature as specified in Figure 1 are taken into account, a contradiction arises: Given that the elliptical answer is resolved to the previous utterance, (12:S.1) asserts If user wants business class, then a business flight from SB to Paris on Sunday is not available, and implicates If user does not want business class, then a business flight from SB to Paris on Sunday is available. Similarly for (12:S.10).</Paragraph>
    <Paragraph position="31"> Thus, the interpretation of a CDCR is that (i) it is now determined whether q or not-q holds, because (ii) the answer (specified in Figure 1) is contingent on c and c is established. Also, (iii) the CDCR indicates the reason for the answer, and (iv) proposes to reconsider the earlier made decision by implicitly re-raising the question whether c holds, and (v) making a suggestion for it to be revised. A negotiation is started in which the conflicting A/V is either revised or confirmed. In the latter case a different solution to the overall goal must be sought.</Paragraph>
    <Paragraph position="32"> As for production, the system may produce a CDCR when (i) answering a yes/no-question whether q, where (ii) the answer is either q or notq, depending on some A/V c which has been established in the context prior to the question whether q. Again, what polarity of CR is more cooperative in a particular context depends on what the preferred answer to the question whether q is assumed to be.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="0" type="metho">
    <SectionTitle>
3 Conditional response dialogue moves
</SectionTitle>
    <Paragraph position="0"> According to the dialogue annotation scheme of (Allen and Core, 1997), utterances in which &amp;quot;the participant does not address the proposal but performs an act that leaves the decision open pending further discussion&amp;quot; are called hold moves. The dialogue moves of a NDCR seem similar to hold in that the answer to q remains pending due to its contingency on an unknown A/V c. Once c is determined, q is answered. Hence, we propose to characterize a NDCR as a dialogue move combining the backward-looking function of a partial yes/noanswer and hold, and the forward-looking function of a yes/no question whether the condition holds. A CDCR is different in that it proposes to reconsider a contexually-determined c. Allen &amp; Core provide no suitable characterization of this. We propose to characterize a CDCR as a dialogue move that combines the backward-looking function of a yes/no-answer with the forward-looking function of an alternative question whether c is preserved or revised.</Paragraph>
  </Section>
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