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<Paper uid="P00-1022">
  <Title>A Computational Approach to Zero-pronouns in Spanish</Title>
  <Section position="4" start_page="0" end_page="0" type="metho">
    <SectionTitle>
3 Zero-pronoun resolution
</SectionTitle>
    <Paragraph position="0"> In this module, anaphors (i.e. anaphoric expressions such as pronominal references or zero-pronouns) are treated from left to right as they appear in the sentence, since, at the detection of any kind of anaphor, the appropriate set of restrictions and preferences begins to run. The number of previous sentences considered in the resolution of an anaphora is determined by the kind of anaphora itself. This feature was arrived at following an in depth study of Spanish texts. For pronouns and zero-pronouns, the antecedents in the four previous sentences, are considered.</Paragraph>
    <Paragraph position="1"> The following restrictions are first applied to the list of candidates: person and number agreement, c-command4 constraints and semantic consistency5. This list is sorted by proximity to the anaphor. Next, if after applying the restrictions there is still more than one candidate, the preferences are then applied, with the degree of importance shown in Figure 1.</Paragraph>
    <Paragraph position="2"> This sequence of preferences (from 1 to 10) stops whenever only one candidate remains after having applied a given preference. If after all the preferences have been applied there is still more than one candidate left, the most repeated candidates6 in the text are then extracted from the list, and if there is still more than one candidate, then the candidates that have appeared most frequently with the verb of the anaphor are extracted from the previous list.</Paragraph>
    <Paragraph position="3"> Finally, if after having applied all the previous preferences, there is still more than one candidate left, the first candidate of the resulting list (the closest to the anaphor) is selected.</Paragraph>
    <Paragraph position="4"> The set of constraints and preferences required for Spanish pronominal anaphora presents two basic differences: a) zero-pronoun resolution has the restriction of agreement only</Paragraph>
  </Section>
  <Section position="5" start_page="0" end_page="0" type="metho">
    <SectionTitle>
4 The usage of c-command restrictions on partial
</SectionTitle>
    <Paragraph position="0"> parsing is presented in Ferrandez et. al. (1998).</Paragraph>
    <Paragraph position="1">  5 Semantic knowledge is only used when working on restricted texts.</Paragraph>
    <Paragraph position="2"> 6 Here, we mean that we first obtain the maximum number of repetitions for an antecedent in the remaining list. After that, we extract the antecedents that have this value of repetition from the list. in person and number, (whereas pronominal anaphora resolution requires gender agreement as well), and b) a different set of preferences. 1) Candidates in the same sentence as the anaphor.</Paragraph>
    <Paragraph position="3"> 2) Candidates in the previous sentence.</Paragraph>
    <Paragraph position="4"> 3) Preference for candidates in the same sentence as the anaphor and those that have been the solution of a zero-pronoun in the same sentence as the anaphor.</Paragraph>
    <Paragraph position="5"> 4) Preference for proper nouns or indefinite NPs.</Paragraph>
    <Paragraph position="6"> 5) Preference for proper nouns.</Paragraph>
    <Paragraph position="7"> 6) Candidates that have been repeated more than once in the text.</Paragraph>
    <Paragraph position="8"> 7) Candidates that have appeared with the verb of the anaphor more than once.</Paragraph>
    <Paragraph position="9"> 8) Preference for noun phrases that are not included in a prepositional phrase or those that are connected to an Indirect Object. 9) Candidates in the same position as the anaphor, with reference to the verb (before the verb).</Paragraph>
    <Paragraph position="10"> 10) If the zero-pronoun has gender  The main difference between the two sets of preferences is the use of two new preferences in our algorithm: Nos. 3 and 10. Preference 10 is the last preference since the POS tagger does not indicate whether the object has both masculine and feminine linguistic forms7 (i.e. information obtained from the object when the verb is copulative). Gender information must therefore be considered a preference rather than a restriction. Another interesting fact is that syntactic parallelism (Preference No. 9) continues to be one of the last preferences, which emphasizes the unique problem that arises in Spanish texts, in which syntactic structure is quite flexible (unlike English).</Paragraph>
  </Section>
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