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<Paper uid="C04-1169">
  <Title>Predicative NPs and the annotation of reference chains</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
3 Discussion
</SectionTitle>
    <Paragraph position="0"> In section 2 we have seen arguments which suggest that non-reflexive predicative NPs are not anaphoric to their subject. First of all, assuming that a predicative NP is coreferential with its subject is not always enough to assign it an interpretation. Secondly, contrary to what one would expect, there is no difference between positive and negative predicative sentences w.r.t. the context-dependency of the predicative phrase. Thirdly, non-reflexive predicative NPs do not have the forms that are expected for nominal anaphora. And finally, non-reflexive predicative NPs behave differently w.r.t. binding than what is expected if they are assumed to be anaphora.</Paragraph>
    <Paragraph position="1"> These facts suggest that the reason why many predicative NPs are intuitively seen as describing the same individual as their subject is a different reason from that which identifies the antecedent of an anaphor. We propose that non-reflexive predicative NPs are not anaphoric to their subject, but rather part of a predication which holds of the subject referent.</Paragraph>
    <Paragraph position="2"> But marking coreference is not necessarily the same as marking anaphor-antecedent pairs, as reference chains can also be thought of in terms of equivalence sets. So does the conclusion that non-reflexive predicative NPs are not anaphoric to their subject mean that one should never annotate predicative NPs as coreferential with their subject when building corpora with reference chains? As far as we can see, that depends on the intended application for the system, on the machine learning system's abilities, and on what additional information is available or retrievable from the corpus and/or the system.</Paragraph>
    <Paragraph position="3"> On the one hand: As long as the machine learning method applied is capable of learning two different systems at once, it may be desirable to include predicative NPs in the same reference chain as their subject, if part of positive sentences. As argued in section 1, predicative NPs in positive sentences do describe the same individual as their subject does, and the semantic information in predicative NPs can be useful for identifying desired later coreferences and ruling out undesired ones. For practical applications it is a goal to collect equivalence classes, and the richer these are, the better.</Paragraph>
    <Paragraph position="4"> The approach is furthermore not very effortdemanding. The drawback of the approach is that it seems to mix two distinct phenomena, i.e. reference tracking and predication. The annotation strategy is therefore theoretically questionable and is likely to lead to unsatisfactory results in some cases, as illustrated by the examples in (3).</Paragraph>
    <Paragraph position="5"> On the other hand: Imagine a system where referentsarenotseenasindividualsintheworld, but abstract entities where e.g. (1) states a berelation between the discourse referent associated with David Beckham and the intensional object corresponding to the second best player in the world. Imagine further that one distinguishes between (discourse) referent tracking and collection of predications. Predicative NPs willonlybeannotatedascoreferentialwiththeir subject if they are reflexive, but any predicative NP will be kept track of as part of a predication that holds of its subject referent. Thus, there are two sources of information about referents; the descriptions used to refer to them, and predications made about them. The latter source will be of importance for reference tracking also independently of predicative NPs. Consider (7).</Paragraph>
    <Paragraph position="6"> (7) Fred drives a taxi, whereas Joe studies math. Who would you prefer to meet, the math student or the taxi driver? The information retrieved from the predications about Fred and Joe is crucial to assign the correct interpretation to the expressions the math student andthe taxi driver. If predications about referents are kept track of just as well as reference chains, then we are in principle able to achieve the correct interpretation for (7).</Paragraph>
    <Paragraph position="7"> Thus, with the present approach, which keeps reference tracking and predication tracking apart, it is not necessary to assume that predicative NPs are coreferential with their sub-ject in order to exploit the important semantic information they may contribute about the sub-ject referent. The present approach is also more theoretically plausible in that it singles out two arguablydistinctphenomena, anditisnotlikely to go wrong in cases like those in (3). The main drawback of this approach is that it is effortdemanding, as it requires a semantic component that keeps track of predications as well as referents. Such a component is not part of most current automatic systems for reference tracking, and without it, the approach produces less information about referents than its competitor described above. For instance, without the componenttokeeptrackofpredications, onedoesn't capture the fact that a predicative NP in a positive sentence is a property of the subject referent, whereas a predicative NP in a negative sentence is not.</Paragraph>
  </Section>
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