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<Paper uid="P84-1085">
  <Title>A SY}~ACTIC APPROACH TO DISCOURSE SEMANTICS</Title>
  <Section position="3" start_page="413" end_page="414" type="intro">
    <SectionTitle>
II THE DYNAMIC DISCOURSE ~DEL
</SectionTitle>
    <Paragraph position="0"> Dealinq with linquistic structures above the clause level is an enterprise which differs in an essential way from the more common variant of linguistic activity which tries to describe the internal structure of the verbal symbols people exchange. Discourse linguistics does not study static verbal objects, but must be involved with the social process which produces the discourse -- with the ways in which the discourse participants manipulate the obligations and possibilities of the discourse situation, and with the ways in which their talk is constrained and framed by the structure of this discourse situation which they themselves created.</Paragraph>
    <Paragraph position="1"> The structure one may assign to the text of a discourse is but a reflection of the structure of the process which produced it.</Paragraph>
    <Paragraph position="2"> Because of this, the Dynamic Discourse Model that we are developing is only indirectly involved in trying to account for the a posteriori structure of a finished discourse; instead, it tries to trace the relevant states of the social space in terms of which the discourse is constructed. This capability is obviously of crucial importance if the model is to be applied in the construction of computer systems which can enter into actual dialogs.</Paragraph>
    <Paragraph position="3"> The Dynamic Discourse Model, therefore, must construct the semantic interpretation of a discourse on a clause by clause basis, from left to right, yielding intermediate semantic representations of unfinished constituents, as well as setting the semantic parameters whose values influence the interpretation of subsequent constituents.</Paragraph>
    <Paragraph position="4"> A syntactic/semantic system of this sort may very well be fromulated as an Augmented Transition Network grammar (Woods, 1970), a non-deterministic parsing system specified by a set of transition networks which may call each other recursively.</Paragraph>
    <Paragraph position="5"> Every Speech Event type, DU type and dcu type is associated with a transition network specifying its internal structure. As a transition network processes the consecutive constituents of a discourse segment, it builds up, step by step, a representation of the meaning of the segment. This representation is stored in a register associated with the network. At any stage of the process, this register contains a representation of the meaning of the discourse segment so far.</Paragraph>
    <Paragraph position="6"> An ATN parser of this sort models important aspects of the discourse process. After each clause, the system is in a well-defined state, characterized by the stack of active transition networks and, for each of them, the values in its registers and the place where it was interrupted. When we say that discourse participants know &amp;quot;where they are&amp;quot; in a complicated discourse, we mean that they know which discourse constituent is being initiated or continued, as well as which discourse constituents have been interrupted where and in what order -- in other words, they are aware of the embedding structure and other information captured by the ATN configuration.</Paragraph>
    <Paragraph position="7"> The meaning of most clause utterances cannot be determined on the basis of the clause alone, but involves register values of the embedding dcu -- as when a question sets up a frame in terms of which its answer is interpreted (cf. Scha, 1983) or when, to determine the temporal reference of a clause in a narrative, one needs a &amp;quot;reference time&amp;quot; which is established by the foregoing part of the narrative (section III B 2). From such examples, we see that the discourse constituent unit serves as a framework for the semantic interpretation of the clauses which constitute the text. By the same token, we see that the semantics of an utterance is not exhaustively described by indicating its illocutionary force and its propositional content. An utterance may also cause an update in one or more semantic registers of the dcu, and thereby influence the semantic interpretation of the following utterances.</Paragraph>
    <Paragraph position="8"> This phenomenon also gives us a useful pert spective on the notion of interruption which was mentioned before. For instance, we can now see the difference between the case of a story being interrupted by a discussion, and the superficially similar case of a story followed by a discussion which is, in its turn, followed by another story. In the first case, the same dcu is resumed and all its register values are still available; in the second case, the first story has been finished before the discussion and the re-entry into a storyworld is via a different story. The first story has been closed off and its register values are no longer avilable for re-activation; the teller of the second story must re-initialize the variables of time, place and character, even if the events of the second story concern exactly the same characters and situations as the first.</Paragraph>
    <Paragraph position="9"> Thus, the notions of interruption and resumption have not only a social reality which is experienced by the interactants involved. They also have semantic consequences for the building and interpretation of texts.</Paragraph>
    <Paragraph position="10"> Interruption and resumption are often explicitly signalled by the occurrence of &amp;quot;discourse markers&amp;quot;. Interruption is signalled by a PUSH-marker such as &amp;quot;incidentally&amp;quot;, &amp;quot;by the way&amp;quot;, &amp;quot;you know&amp;quot; or &amp;quot;like&amp;quot;. Resumption is signalled by a POP- null -markers such as &amp;quot;O.K.&amp;quot;, &amp;quot;well&amp;quot;, &amp;quot;so&amp;quot; or &amp;quot;anyway&amp;quot;. (For longer lists of discourse marking devices, and somewhat more discussion of their functioning, see Reichman (1981) and Polanyi and Scha(1983b).) In terms of our ATN description of discourse structure, the PUSH- and POP-markers do almost exactly what their names suggest. A PUSH-marker signals the creation of a new embedded discourse constituent, while a POP-marker signals a return to an embedding constituent (though not necessarily the immediately embedding one), closing off the current constituent and all the intermediate ones. The fact that one POP-marker may thus create a whole cascade of discourse-POPs was one of Reichman's (1981) arguments for rejecting the AT~ model of discourse structure. We have indicated before, however, that accommodating this phenomenon is at worst a matter of minor technical extensions of the A.&amp;quot;~Iformalism (Polanyi and Scha, 1983b); in the present paper, we shall from now on ignore it.</Paragraph>
  </Section>
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