<?xml version="1.0" standalone="yes"?>
<Paper uid="W02-0212">
  <Title>Conditional Responses in Information-Seeking Dialogues</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> The goal of this paper is to provide a basic account of conditional yes/no responses (CRs): We describe the conditions under which CRs are appropriate, and how these conditions translate into a uniform approach to understanding and producing CRs.1 We focus on information-seeking dialogues between a human user and a dialogue system in the travel domain. We allow for mixed initiative and negotiation to let a dialogue be more collaborative than  &amp;quot;quizzing&amp;quot;. In this context CRs arise naturally (1). (1) U.1: Do I need a visa to enter the U.S.? S.1: Not if you are an EU citizen.</Paragraph>
    <Paragraph position="1"> (2) S.1': Yes, if you are not an EU citizen.</Paragraph>
    <Paragraph position="2"> (1:S.1) is an example of a negative CR, asserting If you're an EU citizen, then you do not need a visa to enter the U.S. An alternative, positive CR is (2:S.1'), asserting If you're not an EU citizen, then you do need a visa to enter the U.S..</Paragraph>
    <Paragraph position="3"> In both cases, the system answers the question (1:U.1), but it makes the answer conditional on the value of a particular attribute (here, citizenship). 1This work was done in SIRIDUS (Specification, Interaction and Reconfiguration in Dialogue Understanding Systems), EC Project IST-1999-10516. We would like to thank Geert-Jan  Kruijff for detailed discussion and comments .</Paragraph>
    <Paragraph position="4"> Moreover, the CR suggests that, for another value, the answer may be different (2).</Paragraph>
    <Paragraph position="5"> The CRs in (1:S.1) and (2:S.1') are elliptical utterances. Intuitively, they can be expanded to the complete propositions in (3) and (30). The material for resolving the ellipsis comes from the immediately preceding context. In the approach we work with, ellipsis is resolved with respect to the current question under discussion (QUD, (Ginzburg, 1996)).</Paragraph>
    <Paragraph position="6">  (3) No, you don't need a visa to enter the U.S. if you are an EU citizen.</Paragraph>
    <Paragraph position="7"> (30) Yes, you do need a visa to enter the U.S. if you are not  an EU citizen.</Paragraph>
    <Paragraph position="8"> The dialogue move of a CR depends on the context. Consider (4) and (5). Similarly to (1), in (4) the system does not know an attribute-value (A/V) on which the positive or the negative answer to the yes/no question is contingent (here, whether the user  wants a business or economy class flight).2 (4) U.1: A flight from K&amp;quot;oln to Paris on Sunday. S.1: I'm sorry, there are no flights from K&amp;quot;oln to Paris on Sunday.</Paragraph>
    <Paragraph position="9"> U.2: Can I fly on Monday? S.2: Not if you want business class.</Paragraph>
    <Paragraph position="10"> S.20: Yes, if you want economy class.</Paragraph>
    <Paragraph position="11"> (5) U.1: I want a business class flight from K&amp;quot;oln to Paris on Sunday.</Paragraph>
    <Paragraph position="12"> S.1: I'm sorry, there are no business flights from K&amp;quot;oln to Paris on Sunday.</Paragraph>
    <Paragraph position="13"> U.2: Can I fly on Monday? S.2: Not if you want business class.</Paragraph>
    <Paragraph position="14"> S.20: Yes, if you want economy class.</Paragraph>
    <Paragraph position="15">  The system's CR (4:S.2) is a request for further information: whether the user wants a business flight (Monday is out), or does not (she is able to fly on Monday). Likewise, (4:S.20) is a request for further information whether the user wants an economy flight (Monday is available), or not (Monday is out). Dialogue (5) is different. Now the user indicates that she is interested in a business class flight 2We realize that intonation might play a role. However, given space restrictions we cannot address this issue here. Philadelphia, July 2002, pp. 84-87. Association for Computational Linguistics. Proceedings of the Third SIGdial Workshop on Discourse and Dialogue, (5:U.1). The system by default assumes that this remains unchanged for another day of travel.</Paragraph>
    <Paragraph position="16"> What both the negative and positive CR in (5) do is to start a negotiation to either confirm or revise the user's decision for business class. The system's response (5:S.2) or (5:S.20) indirectly proposes a change (to economy class) to achieve the higher-level goal of finding a flight from K&amp;quot;oln to Paris on Monday. If the user insists on business class, this goal cannot be achieved.</Paragraph>
    <Paragraph position="17"> If we want a dialogue system to understand and appropriately produce CRs, we need to describe their semantics in terms of the contextual conditions and communicative goals under which these responses occur, and the effects they have on the dialogue context. We aim at providing the basis of an account that can be implementated in the GoDiS dialogue system. GoDis is an experimental system in the travel domain, using the information-state approach to dialogue developed the TRINDI and SIRIDUS projects (Cooper et al., 1999; Lewin et al., 2000). We focus on aspects that can improve its flexibility and functionality.</Paragraph>
    <Paragraph position="18"> Overview. In x2 we discuss the uses of positive and negative CRs in terms of their appropriateness conditions and their interpretation. Inx3 we discuss dialogue moves. We end the paper with conclusions.</Paragraph>
  </Section>
class="xml-element"></Paper>