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What is coreference?

Coreference in the PDT 2.0 Zden ěk Žabokrtský Institute of Formal and Applied Linguistics Charles University in Prague. What is coreference?. multiple expressions in a sentence or document can refer to the same thing. … … John … …. … …. … … …. .. .. … .. he … … .. …. … …. ….. …….

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What is coreference?

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  1. Coreferencein the PDT 2.0Zdeněk ŽabokrtskýInstitute of Formal and Applied LinguisticsCharles University in Prague

  2. What is coreference? • multiple expressions in a sentence or document can refer to the same thing … … John … …. … …. … … …. .. .. … .. he … … .. …. … …. ….. ……. REFERENCE COREFERENCE

  3. Coreference in PDT • links between tectogrammatical nodes • technically: pointer from an anaphor t-node to its antecedent t-node • links can form chains

  4. Two types of coreference • according to Functional Generative Description, two types of coreference distinguished: • grammatical coreference • (partially) determined by grammar rules • textual coreference • determined only by text meaning

  5. Grammatical coreference (1) • relative pronouns • “The man, who…”, “The man, whose …” • typical local configuration: … noun modified by the relative clause main verb of the relative clause … … relative pronoun

  6. Grammatical coreference (2) • reflexive pronouns • in Czech, pronouns referring to clause subject have reflexive form • typical local configuration: … main verb in the clause clause subject … … reflexive pronoun

  7. Grammatical coreference (3) • reconstructed (surface-unexpressed) actor of infinitive verbs • “He started to sing.” “They asked him to come.” • typical local configuration: … control verb … infinitive verb … #Cor.ACT - reconstructed coreferential actor

  8. Textual coreference • anaphors: • personal pronouns • possessive pronouns • reconstructed pronouns (pro-drop)

  9. Special cases • multiple antecedent: • two or more parallel links from a plural anaphor (Peter and Paul … they…) • cataphora • left-to-right links • segm – vague reference to the previous context • exoph - exophora

  10. Amount of data • manually annotated coreference in 50,000 sentences • around 45,000 coreference links

  11. Summary • coreference in PDT 2.0 • one of the largest coreference resources • two types of coreference links • grammatical coreference • textual coreference • anaphors: • pronouns (personal, possessive, relative, reflexive) • reconstructed nodes (pro-drops,actants of infinitive verbs,…)

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