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<Paper uid="E99-1049">
  <Title>Pointing to Events</Title>
  <Section position="3" start_page="0" end_page="0" type="metho">
    <SectionTitle>
2 Background
</SectionTitle>
    <Paragraph position="0"> Generally speaking, events are referred to by pronominal expressions such as that or this: 1  (1) (a) John hated snakes. (b) His neighbour had kept snakes, (c) and he had been bit null from Webber (1991).</Paragraph>
    <Paragraph position="1"> ten by a snake once. (d) This was unfortunate. null The pronoun this in (ld) may refer to the entire situation described by (la) through (lc). But there are other conceivable antecedents for this. The situation described by (lc) may be referred to by this as well, if we consider an alternation of (ld) as in the following: (1') d'. This was quite dangerous.</Paragraph>
    <Paragraph position="2"> The example discourse illustrates that the discourse in (la-c) is organised hierarchically and consists of different discourse segments (e.g. (lac) and (lb-c)). Webber (1991) points out that events are only available for anaphoric reference when they are mentioned by the last utterance (e.g. (lc)) or by the situation that is constructed by the preceding discourse segment (e.g. (1a-c)). The right frontier hypothesis reflects this observation as shown by bold typeset in figure 1. The dis-</Paragraph>
    <Paragraph position="4"> course structure also influences how we conceptualise situations described in a text. In particular, a segment in (la-c) establishes a complex event that can be referred to.</Paragraph>
  </Section>
  <Section position="4" start_page="0" end_page="283" type="metho">
    <SectionTitle>
3 Predictions
</SectionTitle>
    <Paragraph position="0"> Unfortunately, there is much disagreement between theoretical approaches to discourse processing on what exactly is available on the right frontier. The tree structure proposed by Webber, for example, contains the semantic content grouped together for the entire segment.</Paragraph>
    <Paragraph position="1">  'This refers to explanation elaboration segment: (e.g. (2)) (e.g. (3))  between (3b) and (3c) see below): (2) (a) Peter was sitting in his chair at home. (b) All of a sudden, he stood up. (c) The  doorbell had rung. This was...</Paragraph>
    <Paragraph position="2"> Following Webber's account, this can only refer to the situation described by the last utterance (2c) or the situations described by the sentences (2b-c) or (2a-c), but not to (2a) and (2c).</Paragraph>
    <Paragraph position="3"> In contrast, SDRT predicts that the situations described by sentence (2b) or (2c) are available, but not by (2a) nor any combined situation. Consequently, the empirical investigation focuses especially on the question of which described events are available for further attachments and event anaphora depending on the chosen rhetorical relation (i.e. explanation or elaboration).</Paragraph>
  </Section>
  <Section position="5" start_page="283" end_page="283" type="metho">
    <SectionTitle>
4 Experimental data
</SectionTitle>
    <Paragraph position="0"> Six ambiguous sequences such as (2) or (3) were presented to 115 participants. They were asked first to continue the sentences and then to specify explicitly what this referred to.</Paragraph>
    <Paragraph position="1">  (3) Saturday was Jerry's birthday. Several  students organized a dinner for Jerry. Some students had written fancy invitation cards. This was...</Paragraph>
    <Paragraph position="2"> Note that the results as shown by table 1 cannot be explained by either theoretical approach. The results for the explanation relation is best explained by Webber, since either the last mentioned situation or a combined situation of the segments (2b-c) were most often chosen by the participants. On the other hand, results for the elaboration relation contradict the predictions made. The situation described by (3b) should not be available according to Webber's account, instead an ambiguity between (3b) and (3c) can be observed for this sequence. This would be predicted by SDRT. But SDRT cannot explain the combination of two situations that was chosen by subjects 18% of the time for an explanation relation. 2 Results suggest that the type of rhetorical relation has a crucial influence. An explanation relation linking (2b) and (2c) focuses on the sentence describing the cause (i.e. the last utterance), whereas an elaboration relation as in (3) establishes an ambiguous sequence between the last two described situations. In addition, note that a significant proportion of the participants referred to a combined event regardless of the rhetorical relation. null</Paragraph>
  </Section>
  <Section position="6" start_page="283" end_page="283" type="metho">
    <SectionTitle>
5 A computational model
</SectionTitle>
    <Paragraph position="0"> A computational model could benefit from the results presented in this paper. First, the choice of rhetorical relation should affect the way possible antecedents are represented for anaphora resolution. Second, the current data as well as data from reading experiments, for instance, could be used to determine the likelihood of possible attachment sites in the discourse structure.</Paragraph>
    <Paragraph position="1"> However, another question remains: what should the representation of a complex event look like? The tree structure proposed by Webber contains the semantic content grouped together for the entire segment. It seems more plausible that at a higher level of a discourse some form of abstraction takes place.</Paragraph>
    <Paragraph position="2"> Future research must focus on the information that is available from preceding text and what is obtainable for anaphoric expressions such as demonstrative pronouns and definite descriptions.</Paragraph>
  </Section>
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