Definitions
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Coreference: mentions that refer to the same entity
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anaphora: entities come before the word (VS. cataphora)
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Barack Obama said he will sign the bill. In this case he refers to Barack Obama instead of linking to the entity directly
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We wen to see a concert last night. The tickets were really expensive. (Bridging anaphora)
Applications
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Machine Translation: especially for languages that drop pronouns
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Dialogue Systems
Pipeline:
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Mention Detection: pronouns/POS, named entities/NER, or noun phrases/NP
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Coreference resolution
Model Architectures
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Rule-based
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Mention Pair
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Mention Ranking: rank antecedents + NA/Dummy mention
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End-to-end Neural Model:
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word and character embeddings
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Bi-LSTM
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span detection + attention
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calculate a coreference score for each span pair \(i\) and \(j\)
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Clustering: agglomerative clustering
Features used in those models
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Statistical features
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Embeddings
Evaluation
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B-cubed: average of precision and recall of all clusters and gold clusters