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<Paper uid="C94-2129">
  <Title>MODELING DIALOGUE BY FUNCTIONAL SUBCATEGORIZATION</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
1 INTRODUCTION
</SectionTitle>
    <Paragraph position="0"> In task-orientetl dialogues two speakers work in cooperation with the purpose of carrying out a plan.</Paragraph>
    <Paragraph position="1"> This type of interaction has a start and a development structured by the restrictions of space, thne, transaction object and role of the partieipanls.</Paragraph>
    <Paragraph position="2"> A number of researchers \[Grosz and Sidner, 86; Litman and Allen, 87; Ramshaw, 91; I.ambert and Carberry, 9211 have suggested that a coherent discourse consists of segments that are related to one another through some type of structuring relation. Our dialogue model tries to capture the goal-oriented nature of discourse, ideutifing the discourse structure by providing the details of a computational mechanism for recognizing the structural relationships.</Paragraph>
    <Paragraph position="3"> The model enables the incremental recognition of communicative goals using rewriting rules and functional equations. The grammar constructs the structural tree captnring the dialogical functions of the discourse using functional snbcategorization. The subcategorization process improves on previous approaches \[Ferrary et al., 88; Bilage, 91; JOnsson, 911, increasing the expresive power of the traditional dialogue models by modeling the relationships among the communicative actions enabling the task of connecting discottr~.</Paragraph>
    <Paragraph position="4"> The different parts of the system have been implemented using a blackboard architecture. The process starts obUfining the f-slructure associated to the intervention making use of a lexical-functional grammar \[Abaitua ct al., 9111. In a second phase the f-structure is refined providing the correct explanation, essentially it solves the verbal interpretation and obtains referential  information. Then, the planner and/or the dialogue module suu't to work.</Paragraph>
    <Paragraph position="5"> In the remainder of this paper, we will present our dialogue model in a top-down manner. Firstly, we show the exchange structure attoptexl and the subcategorization process using two samples. Then, we explain the retroactive and proactive nature of the interaction and we conclude by presenting two kinds of special interventions, the complex ~lll(l compound interventions.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="814" type="metho">
    <SectionTitle>
2 EXCIIANGE STRUCTURE
</SectionTitle>
    <Paragraph position="0"> We assign to the constituents of the exchange level initiative and reactive ilocutive functions. These functions qualify ctmstituents which are in the same level of structuration. The initiative functions are assigned to the directriee interventions of the exchange.</Paragraph>
    <Paragraph position="1"> The reactive functions constitute the generic class of the answers and they try to satisfy the obligations assumed for the interpretation of the initiative functions.</Paragraph>
    <Paragraph position="2"> Analyzing the corpus that we dispose we have detected the following initiative functions : Fre q, Fre qprel l , Freq_aux, Freq_fic, Fqinlbr m, Fqref and Fqi f. Fre q is a function associated with a petition of achievement a physical action. Fqinlbr m inquires inlonnation about the plan in progress. Fqref and Fqi f demand referential and polar information.</Paragraph>
    <Paragraph position="3"> The above initiative functions are completed with the lollowing reactive functions : Finformre q, Finform, Fiafref and Finfif.</Paragraph>
    <Paragraph position="4"> We assign to the initiative functions, with directrice characteristics, one exchange schema with similar performance to the semantic forms of the verbs in a lexical-functienal context. This exchange schema will tx~ identified from now with the word SCItEMA. An schema specification will exhibit the subcategorizations detected inside an exchange. Therefore, an exchange with au initiative function of type Fqinfor m, inside which a nested exchange has been produced, will have the following schematic representation :</Paragraph>
    <Paragraph position="6"> subcategorized by Fre q and represent preliminaries, auxiliar forms of the request mid fictitious executions of actions.</Paragraph>
    <Paragraph position="8"> Just like in a lexical-functional grammar, the initiative function Fqinfor m subcategorizes to the reactive function Finform and to a subexchange identified by Ecomp. This subexchange has, at the same time, a specific initiative function which subeategorizes to the appropriate reactive function and which is subeategorized by the Fqinfor m function. One example of dialogue sequence where this schema could be applied is the following :  $1.- How does it modify the camera's diafragm ? (Fqinform) $2.- Do you know where is the key for modifying it ? (Fqif) $1.- Yes, in the left part of the camera (Finfi f + Finfref) $2.- Ok, then press the F3 buttom and move the key  towards the left (Finform) In the model which we are going to present both the exchange structure and the intervention structure are going to be definied using rewriting rules. The tree nodes will be enrichied with functional stmcifications just like a lexical-functional grammar. These functional specifications will reference to the initiative and reactive fimctions which are going to appear in the conversation.</Paragraph>
    <Paragraph position="9"> The grammar initialy will have the following rules :  (1) D --&gt; E 1 ............... E i .............. E n (1&amp;quot; EF1)---J, (T EFi)=~ (T EFn)=$ D represents a dialogue, E i the exchange i and EF i the functional specification of the exchange i.</Paragraph>
    <Paragraph position="10"> (2) E i -&gt; I l 12 (I 3)</Paragraph>
    <Paragraph position="12"> Ij represents the intervention j of exchange E i.</Paragraph>
    <Paragraph position="13"> Both F x and Fy represent speech acts of the form F(p).</Paragraph>
    <Paragraph position="14"> That is to say, every node I i will not reflect only the referential and predicative aspect of the interation but also will express the ilocutive force associated to every speech act. A single exchange will be constituted for an initiative intervention and we could suggest nuclear to the exchange, an initiative-reactive intervention and optionaly for a closure reactive intervention of the exchange.</Paragraph>
    <Paragraph position="15"> The functions F x and Fy associated with every constituent will be instantiated for some of the initiative and reactive fimctions introduced before.</Paragraph>
    <Paragraph position="16"> The rule (2) formulated above handles balancod conversational sequences, that is to my, sequences of the following form :  $1(11).- Please, change the exposure mode.</Paragraph>
    <Paragraph position="17"> $2(12).- I changed it already and 1 have left it in PROGRAM.</Paragraph>
    <Paragraph position="18"> $1(13_1).- Ok, let us continue, how can 1 change the speed ? $2(I2).- Press the key XY23 and move the lever.</Paragraph>
    <Paragraph position="19">  The structural-functional tree which would correspond to this dialogue piece would be the one showed in Fig. 1. Structuraly the dialogue fragment would be constituted by two exchanges which inform about the physical actions performed by the speaker and which are connected with a high level task.</Paragraph>
    <Paragraph position="20"> Let us imagine that instead of the previous dialogue piece we produce another one modified a little :  $1(11).- Please, change the exposure mode.</Paragraph>
    <Paragraph position="21"> $2(1&amp;quot;1).- Sorry, how do I change it ? S1(I'2).- Yes, press the buttom MODE and move the lever on the right side.</Paragraph>
    <Paragraph position="22"> $2(12).- I changed it already and i have left it in PR 0 GRAM.</Paragraph>
    <Paragraph position="23"> $1(13).- Ok, let us continue .......</Paragraph>
    <Paragraph position="24">  This second dialogue illustrates a very common phenomena, the speaker departs, momentarily, from the main direction of the conversation, in order to start a secondary exchange which, in most cases, will have a subgoal to be achieved, and then returns to the main axis of the convermtion.</Paragraph>
    <Paragraph position="25"> In order to manager these cases we propose a rule like</Paragraph>
    <Paragraph position="27"> Fig. 2 shows the dialogue structure obtained by means of the aplication of the above rule. We associate the schema 2.a to an exchange which has, like initiative intervention, a request function of achievement physical actions. At the .same time, this function subeategorizes to an subordinate exchange - Ecomp- and a reactive intervention.</Paragraph>
    <Paragraph position="28"> We emphasize that the subordinate exchange Ecomp has a retroactive nature so that it would not appear at the moment of the initial formulation of the schema.</Paragraph>
    <Paragraph position="29"> The schema 2.b is a bit different from the standard notation of a lexical-functional grammar, it specifies an element in the left hand side of the nuclear function. This element will be at the same time the nuclear function of another exchange and reflects the subeategorization that exists between this element and the nuclear constituent of the subordinate exchange.</Paragraph>
    <Paragraph position="30"> The subexchange E&amp;quot; i especified above like E&amp;quot; i --&gt; I&amp;quot; I I'2, can have, of course, nested dialogues defined with the rule E'i--&gt; I&amp;quot; 1 (E'&amp;quot; i) I&amp;quot; 2. Iu our corpus we do not find subdialogues with more than three nested levels very often.</Paragraph>
    <Paragraph position="32"/>
  </Section>
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