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Unformatted text preview: Document Retrieval Docume Docume nt Docume nt Docume nt Docume nt Relevant nt Docs Passage Retrieval passages Answer Processing Dan Jurafsky Passage Retrieval •  Step 1: IR engine retrieves documents using query terms •  Step 2: Segment the documents into shorter units •  something like paragraphs •  Step 3: Passage ranking •  Use answer type to help rerank passages 36 Dan Jurafsky Features for Passage Ranking Either in rule ­based classifiers or with supervised machine learning •  •  •  •  •  •  Number of Named En++es of the right type in passage Number of query words in passage Number of ques+on N ­grams also in passage Proximity of query keywords to each other in passage Longest sequence of ques+on words Rank of the document containing passage Dan Jurafsky Factoid Q/A Document Document Document Document Document Document Answer Indexing Passage Retrieval Question Processing Question Query Formulation Answer Type Detection 38 Document Retrieval Docume Docume nt Docume nt Docume nt Docume nt Relevant nt Docs Passage Retrieval passages Answer Processing Dan Jurafsky Answer Extrac%on •  Run an answer ­type named ­en+ty tagger on the passages •  Each answer type requires a named ­en+ty tagger that detects i...
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This document was uploaded on 02/14/2014.

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