event coreference

**Event coreference** identifies **when different mentions refer to the same event** — recognizing that "the attack," "the incident," and "it" all refer to the same event, enabling coherent event tracking across documents and building unified event representations. **What Is Event Coreference?** - **Definition**: Determine when event mentions refer to same real-world event. - **Example**: "The merger" and "the acquisition" may refer to same event. - **Goal**: Link all mentions of same event for unified representation. **Event Mention Types** **Explicit**: Clear event description ("the earthquake"). **Pronominal**: Pronouns ("it," "that"). **Nominal**: Noun phrases ("the incident," "the tragedy"). **Verbal**: Verb phrases ("happened," "occurred"). **Implicit**: Event implied but not stated. **Why Event Coreference?** - **Information Fusion**: Combine information from multiple mentions. - **Timeline Construction**: Avoid duplicate events in timelines. - **Cross-Document**: Track same event across news articles. - **Knowledge Graphs**: Create unified event nodes. - **Summarization**: Avoid redundant event descriptions. **Coreference Signals** **Lexical**: Same or similar words ("attack" / "assault"). **Temporal**: Same time references. **Spatial**: Same location. **Participants**: Same entities involved. **Event Type**: Same event category. **Discourse**: Pronouns, definite descriptions. **Challenges** **Ambiguity**: Similar events that are actually different. **Granularity**: Is "World War II" one event or many? **Cross-Document**: Matching events across sources. **Partial Overlap**: Events that partially overlap. **Implicit Mentions**: Recognizing implicit event references. **AI Techniques**: Clustering, pairwise classification, graph-based methods, neural coreference models, joint entity-event coreference. **Applications**: Multi-document summarization, news aggregation, knowledge base construction, question answering, event tracking. **Datasets**: ECB+, KBP Event Nugget, TAC-KBP Event Track. **Tools**: Research event coreference systems, extensions of entity coreference tools.