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<Paper uid="C94-2196">
  <Title>l)iscourse and Deliberation: Testing a Collaborative Strategy</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> A discourse slralegy is a strategy for communicaling with another agent. Agents make slrategy choices via decisions abotlt whetl 1o talk, when 1o let tile olher agenl talk, wllal Io say, aiR\[ how to say il. ()no choice a COllVelSitliOllal i:lgelll lnllst make is whether ~ltl utterance sholdd include some relev~ml, but Olllional, information in what is communicated. For ex~unple, consider 1: 1) a. Let's walk along Wahlut St.</Paragraph>
    <Paragraph position="1"> b. ll's shorter.</Paragraph>
    <Paragraph position="2"> The speaker made a shategic choice in 1 to include lb since she could have simply said la. What detemlines the speaker's choice? Existing dialogue systems have two modes lot dealing with optional inlormalion: (1) includeall optional inlormatiou thai is not already known lo the he, e'er; (2) include no optional inlommlion IMoore and l'aris, 19931. Bul Ihese modes are simply the extremes of possibility ~md Io my knowledge, no l)revious work has proposed any principles for when Io include oplional fillornmtion, or any way of lesting the i)roposcd l/rinciples lo see how lhey are affecled by the conversants and their processing ahilities, by the task, by tile COtTllntlnication channel, or by the domain.</Paragraph>
    <Paragraph position="3"> This lmper presenls a new experimeillal melhod for determining whelher a discourse strategy is effective and presents experimenlal results on a slralegy for supporling deliberalion. Tile ntethod is b~tsed on earlier simulation work by Carletla and Pollack ICarletla, 1992; Pollack ~md Ringuelle, 1990\]. Section 2 outlines hypotheses about the factors that affect which strategies are effective. Section 3 presenls a new inelhod for testing lhe role el'the *This research was parlially futlded by AR() grant  I)AAI A) J,-gg-C0031PI.~I and 1 )A RPA grant N00014-90-J- 1863 at Ihe University o f l'ennsylwmia and by \[ lewlcit l'ackard, U.K. hypothesized factors. &amp;quot;File experimental results in section 4 show that effective stralegies 1o supporl deliberation are determined by bolh cognilive and lask variables.</Paragraph>
    <Paragraph position="4"> 2 Deliberation ill l)iscourse  l)Niberation is file process by which an agent decides what to believe and what to tit&gt; \[G~dliers, 199 l; Doyle, 19921. ()he slralegy that supports deliberation is the ExpliciI-Warrant strategy, as in 1. The WARRANT in lb can be used by the he~uer in deliberating whether lo ACCEPT or REJIi(?T tile speakef's I'ROPOSAI, in la. 1 An amdysis of proposals in a corpus of 55 problem-solving dialogues SllOWS lhat communicating agents don't always include warrants in a prol)osal, and suggest a number of hypolheses abotlt which factors alfecl lheir decision I Walker, 1993; Pollack el al., 19821.</Paragraph>
    <Paragraph position="5"> Consider a situalion in which an agent A w~mts ~u~ agent B to accept a proposal P. If B is a 'helpful' agent (llOllaHl.Ol)Ol/lOtlS), B will accepl A's proposal withoul a wammt. Altemalively, if B deliberates whether to accept 1; but B knows of no competing options, Ihen P will be the best el)lion whether or not A lells P, the WatW~Ult lor P. Since a w~u','ant makes the dialogue longer, tile Explicit-Wml'~mt strategy might be inefficient whenever either of these situalions hold.</Paragraph>
    <Paragraph position="6"> Now consi(lel a silualiOll where P, is HI) atltOllOlllO|lS agenl I Galliers, 19911. B always deliberates every proposed and B probably knows of oplions which compete with proposal P. Then B c~umot decide whelher to accept P withoul a warrant. Supposedly agenl A should omit a warrant is if it is ah'eady believed by B, so that the speaker in 1 woukl not have said It's shorter if she believed that the hem'or knew that file Wahlul St. mute was shorter. However, consider 2, said in discussing which Indian reslaurant to go to for hmch: (2) a. Listen to Ramesh.</Paragraph>
    <Paragraph position="7"> b. tle's lndiau.</Paragraph>
    <Paragraph position="8"> The w~m~Ult in 217 was included despite tile facl that il was cOlnlllOll knowledge ;llllOng lhe COl)VelSalltS. Its inclusion violates the rule of Don't tell people facts that they already k#tow. ~= Clearly lhe rule does not hold.</Paragraph>
    <Paragraph position="9"> I The telalion between a WARRANT and the PR(II,OSI{ COlllmunicative act is similar to the MOTIVATION relation of \[Moore and Paris, 1993; Mann and Thompson, 1987\]. A WARRANT is always optional; this is consistent with the RST fl'anlewolk in which all satellites are optional information.</Paragraph>
    <Paragraph position="10">  These aheady-known w~u'rants m'e a type of INFOR-</Paragraph>
  </Section>
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