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<Paper uid="C90-3076">
  <Title>Three Typed Pragmatics for Dialogue Structure Analysis</Title>
  <Section position="3" start_page="0" end_page="370" type="metho">
    <SectionTitle>
2. THREE TYPED PRAGMATICS
</SectionTitle>
    <Paragraph position="0"> Three types of universal pragmaties (el.</Paragraph>
    <Paragraph position="1"> LevinsonS3) can be classified and described by the following plans: Interaction-Plan - a plan basically eharaeterized by a dialogue turntaking*(2) which describes a sequence of communicative acts*(3), Communication-Plan a plan which determines how to execute or  achieve an utterance goal or dialogue goals, and Dialogued:qan : a plan for establishing a dialogue construction, e.g. a cooperative dialogue*(4).</Paragraph>
    <Paragraph position="2"> For example, in order to achieve the goal of registering for the conference tim following sequer, ce must usually be performed (Domain-Plan}: obtain a registration form, fill out the form and return it to the secretariat. In such a telephone dialo}'ue, if something is needed to execute the gore action, a request to send it can be made, or it will be offered to you (Co:mmunication-t)lan). To complete the cooperative infbrnmtion-seeking, the hearer will resl)ond to the speaker's request*(5) (Interaction-Plan). Beiorc building a whole dialogue structure, the speaker should utter the opening section of the dialogue, especially on the telephone. Furthermore when the dialogue is finished, the speaker should wide up the dialogue (Dialogue-Plan).</Paragraph>
    <Paragraph position="3"> Each plan is described in terms of a schema formulation (plan-schema).</Paragraph>
    <Paragraph position="4"> A plan-schema has various slots to describe both an action's inner properties, e.g. HEADER and</Paragraph>
    <Paragraph position="6"> between the action and prerequisite states/actions, effects, etc., e.g. PREREQUISITE, DECOMPOSITIONS, CONSTRAINTS, EFFECTS.</Paragraph>
    <Paragraph position="7"> A definite hierarchical order among these plans is available as follows;</Paragraph>
    <Paragraph position="9"/>
  </Section>
  <Section position="4" start_page="370" end_page="370" type="metho">
    <SectionTitle>
3. DIALOGUE ANALYSIS
</SectionTitle>
    <Paragraph position="0"> There are several linguistic phenomena which are hard to interpret, such as ellipses, referring pronouns and substitutional expressions. Both information from the established context and expectations from the current dialogue situation are required to resolve such problems. In order to get these information a dialogue structure which indicates the goal hierarchy of utterances in a dialogue must be constructed. A dialogue analysis is required and it is necessary to determine ; (1) how to infer each goal of an utterance within a dialogue, (2) how to make clear the relationships between goals within the dialogue.</Paragraph>
    <Paragraph position="1"> For the first problem, a plan recognition inference method is adequate for identifying an utterance intention because the intention can be inferred by recognizing the speaker's plan by chaining communicative acts regarded as speech acts in a specific domain \[Allen80), \[Perrault80\], \[Litman 87\]. For the second problem, the *(4) :A dialogue global construction usually has an opening section and closing section. I lere, such a linguistic phenotmnon is regarded as language-universal.</Paragraph>
    <Paragraph position="2"> *(5) :On the other hand, in order to complete the cooperative interaction, when the speaker imparts information, the hearer will confirm what the speaker has said according to the speaker's belief in the hearer's intention.</Paragraph>
    <Paragraph position="3"> *(6) An active chart parser has been developed for Japanese dialogue analysis on a unification based grammar, which is based on IIPSG and JPSG \[Pollard88), \[Gunji87\], \[Kogure89\]. Furthermore, many discourse entities can be identified by using NP Identification Method \[Nogaito88\]. domain..specific, knowledge is related to the action and objects, especially the action hierarchy which is used to grasp the utterance ~ oal, and three kinds of pragmatics between unmns involved in a spoken dialogue are used to grasp the dialogue development.</Paragraph>
  </Section>
  <Section position="5" start_page="370" end_page="370" type="metho">
    <SectionTitle>
3A Communicative Acts
</SectionTitle>
    <Paragraph position="0"> First, in order to recognize the speaker's plan, it is necessary to recognize the turn-taking patterns. Communicative acts \[Cohen84\] are introduced . In Fig.l, an example of communicative acts in a cooperative task-oriented dialogue, e.g. 'queries and explanations regarding registration for an international conference' is shown.</Paragraph>
    <Paragraph position="1"> A communicative act in the demand class and a corresponding act in the response class make a turn-taking pair. This is recognized by the interaction plan. A communicative act is a decomposition element of an interaction plan.</Paragraph>
    <Section position="1" start_page="370" end_page="370" type="sub_section">
      <SectionTitle>
3.2 Inference Mechanism
</SectionTitle>
      <Paragraph position="0"> 'An utterance meaning is represented by illocutionary speech act types and propositional contents obtained from a tlead-Driven unification-based active chart parser*(6) for Japanese dialogues. The parsing result is described by a feature structure and tim system input is modified into a communicative act with propositional contents. These consist of a certain predicate, an 'utterance type', and some variables, in particular, 'speaker', 'hearer', and 'topic'. 'Topic' is, on a surface level, an NP marked with the Japanese special particle, 'wa', or the compound particle 'nituite'.</Paragraph>
      <Paragraph position="1"> The plan recognizer (1) assumes a goal. (2) If a particular goal cannot be found, then stop else goto next (3). (3) Infer a chaining path from an input to the goal. If success, stop. Else return to the first process (1) in order to try to find the next candidate. The chaining process between plans generally finds a candidate plan from the current state (IIEADER) to an action list represented in I)ECOMPOSITtON. Ilowever if this fails, the chaining will be continued in accordance with PREREQUISITE and EFFECT.</Paragraph>
      <Paragraph position="2"> In order to manage the current understanding state, the system uses two slacks.</Paragraph>
      <Paragraph position="3"> UN1)ERSTANDING-IAST stores completed plans as the current understanding state, and GOAL-IAST maintains incomplete plans regarded as possibilities and expectations for -2- 371 future goals . An overview of a dialogue structure construction process is shown in Fig.2.</Paragraph>
    </Section>
  </Section>
  <Section position="6" start_page="370" end_page="370" type="metho">
    <SectionTitle>
4. AN EXPERIMENTAL SYSTEM
</SectionTitle>
    <Paragraph position="0"> This analysis model is realized by using lout&amp;quot; typed plans which are categorized into Ulree types of universal pragmatics and a type oPS task-dependent knowledge related to common action hierarchies. The system has been implemented in Symbolics Common Lisp. A dialogue structure is represented by both completed plans and incomplete plans stored in the two stacks.</Paragraph>
    <Paragraph position="1"> Therefore, the system can understand dialogue meanings and can offer a dialogue structure using the contents of both stacks. Four model dialogues regarding an international conference registration taken from slightly modified interkeyboard dialogues in Japanese have been applied. For example, the system can understand a Japanese substitutional expression, e.g. &amp;quot;Oisog-i kudasai&amp;quot; (literal translation : 'Hurry please') which shows no agent, no object and no verb, because the current topic which is focused on an action in the domain plan is known in the system and the omitted verb (e.g. 'Return-Form') can be identified under the scope dominated by the topic.</Paragraph>
  </Section>
  <Section position="7" start_page="370" end_page="370" type="metho">
    <SectionTitle>
5. CONCLUSION
</SectionTitle>
    <Paragraph position="0"> Litman &amp; Allen introduced a set of discourse plans, each one corresponding to a particular way that an utterance can relate to a discourse topic. They distinguish discourse plans from a set of domain plans. The dialogue structure analysis model basically follows the above idea and uses new three typed pragmatics: interaction plan, communication plan and dialogue plan. By introducing these plans, the mech~mism for constructing a dialogue structure becomes - clear because of the way a surface utterance is connected with both pragmatics and the domain-specific knowledge, and by reducing the search space using a hierarchical order of applying knowledge, computational efficiency is improved.</Paragraph>
  </Section>
  <Section position="8" start_page="370" end_page="370" type="metho">
    <SectionTitle>
Acknowledgement
</SectionTitle>
    <Paragraph position="0"> The authors would like to thank The President Dr. Akira Kurematsu and our other colleagues at ATR Interpreting Telephony Research Laboratories for their encouragement and thought-provoking discussions.</Paragraph>
  </Section>
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