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<Paper uid="C92-4180">
  <Title>PREFERRED ARGUMENT STRUCTURE FOR DISCOURSE UNDERSTANDING</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
1. Introduction
</SectionTitle>
    <Paragraph position="0"> The main purpose of communication is to exchange intbrmation. On the part of a speaker, he may employ various strategies to organize the information he intends to couvey, in that some bear old information while others carry new information. Therefore, a discourse understanding model should be able to process the flow of information throughout the entire text. In this paper, our issue is tbcused on the referring arguments in Chinese narrative discourse, and our main concern is how they are structured in relation to infom~ation flow.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="0" type="metho">
    <SectionTitle>
2. Preferred Argument Structure in
Chinese Narrative Discourse
</SectionTitle>
    <Paragraph position="0"> Unlike the languages Du Bois has studied (1987), Mandarin Chinese is a typologically different language with no inflection and relatively free word order. Nevertheless, it still exlfibits its own idiosyncratic PAS in spoken narrative discourse. The corpus for the present study comprises eight oral narratives as told by eight Mandarin native speakers of 20-25 years old. They were requested to describe the story about thc popular movie Ghost to the interviewer in a speech laboratory. It portrayed AcrEs DI3 COLING 92, NAV,'II!S, 23-28 aOl':r 1992 1 1 4 2 PROC. OF COL1NG-92, NhNrF.s, AUG. 23-28, 1992 a young man who was killed accidentally in a robbery, and who tried to protect his girlfiiend from file nmrderers and to take revenge on them in form of a spirit. The uarratives were taped for later transcription.</Paragraph>
    <Paragraph position="1"> To study the Chinese PAS, our examination is focused on the issues of quantity and role iu distributing lexical arguments and new referents across grammatical positions at both the grammatical and pragmatic dimensions.</Paragraph>
    <Section position="1" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
2.1 Preliminaries for Analysis
</SectionTitle>
      <Paragraph position="0"> Segmentation of the 120 minutes long narratives was subject to intonation unit being identified by eat' as at stretch of speech uttered under a single coherent intonation contour and typically bounded by a pause. Chafe (1987) hlts hypothesized that intonation units representing linguistic expressions of focuses of consciousness are independent processing units typical of spoken discourse. In the present corpus, there were a total of 1433 intonation units, with a mean length of 6.69 words. The fact that the clause being defined as a verb and its arguments, and the intonation unit often coincide (Du Bois, 1987; Chafe, 1987, 1988) was further confirmed in this study, sittce 85.28% (1222) intonation units contained clausal elements. Those units comt~rised false starts, repetitions, filled pauses, as well as clause fragments such as conjunctions, adverbials, and particles would be excluded from further analysis. Therefore, tile study of Chinese PAS is indeed based on chmses.</Paragraph>
      <Paragraph position="1"> Following is a sample of five clausal intonation units (a-e) produced by a female speaker: (1) a. jiouyitian ta genzhe ta nupengyou one day he follow his girlfriend 'One day, he followed his girlfriend.' b. zai ta nupengyou ji~di deshihou in bis girlfriend home when 'When (he was) in his gMfriend's tlome,' c. la nupengyou zcd huan yifu his girlfriend PROG change clothes 'his girlfriend was changing clothes.' d. ranhou you yi ge huztiren then there-be one CI~ bad guy 'Then, there was a bad guy.' e. huairen chuang finial bad guy break in 'The bad guy broke in.' Within a single clause, the molphological type of each referent, its gramnlatical role, as well as information status were all recorded. The morphological type of an overt referent in Chinese was either a lexical NP or a pronoun, whose surface grammatical role would be classified as A (transitive subject), S (intransitive subject), O (transitive object), or Oblique (object of a preposition). Furthermore, Chafe (1987)'s three-way distinction of information tbr referents was adopted, mainly because his categories lay their foundation on the actual cognitive processing of information transfer by language users. They were given information, accessible information, and new information. A given referent referred to the entity mentioned previously, while a new refi~rent was the one that had uot yet been brought up in the prior context. Internlediate between these two was accessible information, either coming from the expectations associated with a schema or resulting ti~om deactivation from an earlier state. Following Du Bois (1987), a referent constituted by deactivation should be at least twenty propositions away from its most recent appeluance operationally.</Paragraph>
    </Section>
    <Section position="2" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
2.2 The Grammatical Dimension of PAS
</SectionTitle>
      <Paragraph position="0"> The purpose of studying PAS at the grammatical dimension is to examine whether there is a prefen'ed surface configuration of arguments in the observed data. Therefore, we investigate both the number of lexical (NP) argmnents and their distribution across the granunatical roles in clauses.</Paragraph>
      <Paragraph position="1"> According to our tabulation shown in Table I, of the 1127 clauses (excluding the equational type), those with zero or one lexical argument are the most common structure which constitute a distinct majority (94.15%).</Paragraph>
      <Paragraph position="3"> Since only transitive verbs can take more than one argument, it is necessary to seperate them from the intransitive ones for tabulation, in ca~ the rarity of two-lexical-argument structures is simply due to tile rmity of transitive clauses.</Paragraph>
      <Paragraph position="4"> The result in &amp;quot;Fable 2 shows clearly that even in transitive constructions, two-lexical-argument structures are still a minority (9.17%). \]'he result indeed supports Du Bois's One Lexical Arguanent Cot~'traint in that &amp;quot;there is a tendency for speakers to avoid more than one lexical</Paragraph>
      <Paragraph position="6"> Since speakers incline to use one lexical argument at most in a single clause, it is necessary to study whether this single lexical referent is randomly distributed across the grammatical roles. According to our tabulation as shown in Table 3, it is realized that O (84.3%) and Oblique (92.31%) each contain an overwhelming proportion of lexical arguments, whereas A and S contain a smaller portion of them.</Paragraph>
      <Paragraph position="8"> Since 64.56% of all referents are lexical, if they are randomly distributed across the grammatical positions, 38.98% of them will appear in the O role, while the A and S roles are restricted to include lexical referents, as indicated by Table  to avoid lexical referents appearing in the A position, Chinese speakers would not prefer the A and S roles to mention a referent lexically. It is the position O (or Oblique) that preferentially favors lexical arguments. The Lexical 0 Constraint is thus proposed to characterize this particular phenomenon in Chinese narrative discourse. In short, the One Lexical Argument Constraint and the Lexical 0 Constraint, which are indeed the constraints on quantity and role respectively, constitute the Chinese PAS at the grammatical dimension. The quantity of lexical argument within a clause is usually one at most, and this single argument preferentially appears in the O role. Although they are not categorical rules, they do represent a statistically significant tendency of actual language use.</Paragraph>
    </Section>
    <Section position="3" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
2.3 The Pragmatic Dimension of PAS
</SectionTitle>
      <Paragraph position="0"> In the preceding section, it has been shown that in narrative discourse different argument positions of a clause have distinct morphological preferences. This section aims at studying the pragmatic dimension of PAS by examining the quantity of new arguments, as well as their distribution across the grammatical roles.</Paragraph>
      <Paragraph position="1"> Firstly, it is found that transitive and intransitive clauses either contain zero or one new referent, with the former predominating (81.06%), as indicated by Table 5.</Paragraph>
      <Paragraph position="2"> Significantly, not a single clause contains two new referents. The result supports Du Bois's One New Argument Constraint to &amp;quot;avoid more</Paragraph>
      <Paragraph position="4"> To understand whether the single new referent is randomly distributed across A, S, O, and Oblique, it is necessary to examine the distribution of information across these positions. As indicated in Table 6, a substantial proportion of A and S carry old information, and new referents preferentially occur in O and Oblique.</Paragraph>
    </Section>
  </Section>
  <Section position="5" start_page="0" end_page="0" type="metho">
    <SectionTitle>
ACRES DE CO\[3NG-92, Nar~q'Es, 23-28 AO(JT 1992 1 1 4 4 Paoc. ov COLING-92, NANTES, AUG. 23-28. 1992
</SectionTitle>
    <Paragraph position="0"/>
    <Paragraph position="2"> Of 239 new referents found in the corpus, a large portion occur in the O role (51.05%) as shown in Table 7, while only a small portion appear in the A and S roles which overwhelmingly convey old information. Since Chinese speakers disfaw)r both the A and S roles to mention a new referent, Du Bois's Given A Constraint, which &amp;quot;avoids introducing a new referent in the A-role argument position&amp;quot; (p.827), is inappropriate to Chinese narrative discourse. The New 0 Constraint is then proposed for Chinese to characterize the free occurrence of new referents in the O role, as well as the high restriction in the A and S roles. Tahte 7. Distribution of new arguments</Paragraph>
    <Paragraph position="4"> Comparing the frequency distribution of A and S, it is even rare for A to code new referents.</Paragraph>
    <Paragraph position="5"> This can be explained by the fact that Chinese includes a type of presentative construction which &amp;quot;performs the function of introducing into a discourse a norm phrase naming an entity&amp;quot; (Li &amp; Thompson, 1981). Verbs of this sentence type are usually intransitive, and the following arguments usually carry new information. Since speakers do not necessarily use presentative constructions to introduce a new entity, they merely constitute a minority (20 clauses) in our corpus, as exemplified in (2) and (3).</Paragraph>
    <Paragraph position="6"> (2) turan you yi ge huairen paocludaiqiangjie suddently exist one CL bad guy run out mb 'Suddently, there is a bad guy mnning out to rob.' (3) fie shang you yi ge zhaopai ya street on exist one CL signboard PART 'On the street, there is a signboard.' In short, the One New Argument Constraint and the New 0 Constraint constitute the Chinese PAS at the pragmatic dimension.</Paragraph>
    <Paragraph position="7"> There is a strong tendency in discourse to limit the number of new ~ugument in a clause to a maximum of one. This single new referent tends to be introduced in the O (or Oblique) role and the second occurrences preferentially appear in the A and S roles. It is of course this preponderance of old information found in the {A, S} alignment that gives Chinese the distinction of being a topic-prominent language.</Paragraph>
    <Section position="1" start_page="0" end_page="0" type="sub_section">
      <SectionTitle>
2.4 Correlation of PAS between Gram-
matical and Pragmatic Dimensions
</SectionTitle>
      <Paragraph position="0"> We have already studied the quantity and the role constraints that constitute PAS for Chinese narrative discourse at both the grammatical and pragmatic dimensions. The correlation of PAS between these two dimensions is so strong that the grammatical One Lexical Argument Constraint and Lexical 0 Constraint are parallel to the pragmatic One New Argument Constraint and New 0 Cor~traint respectively, as shown in Table 8. In other words, the most preferred structure is to have one new argument at most within a single clause. Since new referents in Chinese have to be coded in full NP form, it is thus less likely to include more than one lexical argument within one discourse unit. Moreover, there is a strong tendency for the single new argument to appear in the O role, so that the lexical referent typically appear in this particular position. The flow of information does have a corresponding grammatical patterning.</Paragraph>
      <Paragraph position="1">  Comparing the Chinese PAS with the one Du Bois proposed for the languages he has studied such as Sacapultec Maya, as shown in Table 9, it is obvious that Du Bois's PAS cannot completely be generalized to Chinese, at least the narrative discourse genre is concerned. Their difference lies in the distribution of lexical ACRES OE COLING-92, NANII~S, 23-28 AOI\]T 1992 1145 PROC. OF COLING-92, NANTES, Ant;. 23-28, 1992 arguments and new referents across grammatical roles. As the PAS in Sacapultec avoids mentioning new lexical arguments in the A role, Chinese speakers disfavor both the A and S roles and strongly prefer O.</Paragraph>
      <Paragraph position="2">  Chinese, like a number of other languages whose pattern of information flow in spoken narrative discourse has been investigated to date, also exhibits PAS. This suggests that there is a strong discourse pressure driving the various grammatical patterning in different languages, so that the universality of the PAS Du Bois proposed encounters challenge.</Paragraph>
      <Paragraph position="3"> However, from the computational point of view, no matter whether PAS is universal or language-specific, its existence has significant implication to discourse understanding, in that the flow of information throughout a connected discourse is highly structured with a corresponding grammatical patterning as far as quantity and role are concerned. Therefore, it is possible to identify the information status of an argument by virtue of grammatical analysis, so that both grammatical and pragmatic processing can be carried out simultaneously. Even though PAS is not categorical in nature, a discourse understanding model can still use it as heuristic device to process the information structure of a connected spoken discourse.</Paragraph>
      <Paragraph position="4"> In short, a discourse understanding model employing PAS for information processing should take the following points into consideration:  (a) Clauses are the basic information processing units.</Paragraph>
      <Paragraph position="5"> (b) Transitive and intransitive clauses should be seperated for analysis.</Paragraph>
      <Paragraph position="6"> (c) The morphological type, grammatical role,  and information status should he recorded for each argument position.</Paragraph>
      <Paragraph position="7"> (d) The quantity and role constraints are the heuristic principles for information processing.</Paragraph>
    </Section>
  </Section>
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