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<Paper uid="E83-1031">
  <Title>Wolfgang Wahlster FBI0 - Angewandte Mathematlk</Title>
  <Section position="3" start_page="0" end_page="188" type="intro">
    <SectionTitle>
1. INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> Frequently a questioner expects more than a direct, literal response although he must assume that the answerer is not informed about what particular information he is seeking. The questioner imputes to a cooperative dialogue partner the communicative competence to reply to a simple yes-no question like (I) with an extended response (cf.</Paragraph>
    <Paragraph position="1"> (12\], (11\]) like (la) rather than with a simple Yes.</Paragraph>
    <Paragraph position="2"> (I) Are you going to travel this summer? (la) Yes, to Sicily.</Paragraph>
    <Paragraph position="3"> In the absence of special information about the previous course of the dialog or the intentions of the questioner (the unmarked case) an answer like (la) seems more appropriate than (Ib) or (Ic).</Paragraph>
    <Paragraph position="4"> (Ib) Yes, with an old school friend.</Paragraph>
    <Paragraph position="5"> (Ic) Yes, by plane.</Paragraph>
    <Paragraph position="6"> OF course, there are numerous dialog situatlons in which (lb) os&amp;quot; (lc) could be generated as a communicatively adequate response on the basis of a par. t+-cular partner model. But it still must b~ asked why in dialogs of the type 'information ,upply' the unmarked response takes the form (la) ~nd not (lh) or (lc).</Paragraph>
    <Paragraph position="7"> In this paper we will present the results of a computational study of this problem for the domain Research on HAM..ANS Is currently being supported by the German Ministry of Research and Technology (8MFT) under contract 081T15038 'locomotion verbs' in dialogs based on a visually present world of discourse. This question is particularly important for the construction of cooperative dialo 9 systems, since, in many applications, no explicit knowledge about the dialog goals of the questioner is available at the outset. If a,system is nevertheless expected to 'over-answer , i.e. to volunteer information that has not specifically been requested, it must command a set of heuristic criteria for selecting the additional information that is to be verbalized \[111.</Paragraph>
    <Paragraph position="8"> It is noteworthy that the three additional points of information in (la), (lb), (1c) correspond to filled deep case slots of the verb used in the question (GOAL, CO-AGENT and INSTRUMENT, respectively). This suggests that the unfilled optional case slots in the question are candidates for additional information. For a question like (2), in which all the deep case slots of 'break' are filled, only a direct response like (2a) is to be expected as a positive answer, while in (3), where only the obligatory deep case slots are filled, an extended response like (3a) can be expected.</Paragraph>
    <Paragraph position="9">  (2) Did you break the window with your slingshot yesterday? (2a) Yes.</Paragraph>
    <Paragraph position="10"> (3) Did you break the window? (3a) Yes, with my slingshot.</Paragraph>
    <Paragraph position="11">  Since not every optional deep case of a given verb unspecified in the question is suitable for an unmarked extended response (e.g. (la)-(lc)) we may define the problem more precisely by asking which of the deep case slots unspecified in the question are to be chosen as the unmarked values.</Paragraph>
    <Paragraph position="12"> For our domain Of investigation 'locomotion verbs' let us consider questions (4) and (5), which refer to a visually present world of discourse. In each case perceptual processes are assumed as a prerequisite for the answer.</Paragraph>
    <Paragraph position="13">  4) Which vehicle stopped? &amp;a) The bus, on Hartungstreet.</Paragraph>
    <Paragraph position="14"> 4b) The bus, because the driver stepped on the brake.</Paragraph>
    <Paragraph position="15"> 5) Did the bus turn off? 5a) Yes, from Hartungstreet onto Schlueterstteet. 5b) Yes, together with the taxi cab.</Paragraph>
    <Paragraph position="16"> The instantiation of the iocatlve slot in answer (4a) and the source and goal slots in (Sa) is predictable in contrast to the causative slot in (4b) and the co agent slot in (5b). As examples (4) and (5) demonstrate, the same optional deep case slot is not always selected as the unmarked  option. The choice is dependent upon the verb contained in the question. Moreover, {Sa) shows that combinations of deep cases are possible in unmarked extended responses, In the area under investigation here, the following heuristic carl be employed to determine the</Paragraph>
  </Section>
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