124.11.lec7

124.11.lec7 - CS 124/LINGUIST 180 From Click to edit Master...

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Click to edit Master subtitle style 1/10/09 Dan Jurafsky Lecture 7: Named Entity Tagging Thanks to Jim Martin, Ray Mooney, and Tom Mitchell for slides
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6/1/11 Outline Named Entities and the basic idea BIO Tagging A new classifier: Logistic Regression Linear regression Logistic regression Multinomial logistic regression = MaxEnt Why classifiers aren’t as good as sequence models A new sequence model: MEMM = Maximum Entropy Markov Model
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6/1/11 Named Entity Tagging Slide from Jim Martin 3 CHICAGO (AP) — Citing high fuel prices, United Airlines said Friday it has increased fares by $6 per round trip on flights to some cities also served by lower-cost carriers. American Airlines, a unit AMR, immediately matched the move, spokesman Tim Wagner said. United, a unit of UAL, said the increase took effect Thursday night and applies to most routes where it competes against discount carriers, such as Chicago to Dallas and Atlanta and Denver to San Francisco, Los Angeles and New York.
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6/1/11 Named Entity Tagging CHICAGO (AP) — Citing high fuel prices, United Airlines said Friday it has increased fares by $6 per round trip on flights to some cities also served by lower-cost carriers. American Airlines , a unit AMR , immediately matched the move, spokesman Tim Wagner said. United , a unit of UAL , said the increase took effect Thursday night and applies to most routes where it competes against discount carriers, such as Chicago to Dallas and Atlanta and Denver to San Francisco, Los Angeles and New York. Slide from Jim Martin 4
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6/1/11 Named Entity Recognition Find the named entities and classify them by type. Typical approach Acquire training data Encode using IOB labeling Train a sequential supervised classifier Augment with pre- and post-processing using available list resources (census data, gazeteers, etc.) Slide from Jim Martin 5
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6/1/11 Temporal and Numerical Temporals Find all the temporal expressions Normalize them based on some reference point Numerical Expressions Find all the expressions Classify by type Normalize Slide from Jim Martin 6
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6/1/11 NE Types Slide from Jim Martin 7
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6/1/11 NE Types Slide from Jim Martin 8
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6/1/11 Ambiguity Slide from Jim Martin 9
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6/1/11 NER Approaches As with partial parsing and chunking there are two basic approaches (and hybrids) Rule-based (regular expressions) Lists of names Patterns to match things that look like names Patterns to match the environments that classes of names tend to occur in. ML-based approaches Get annotated training data Extract features Train systems to replicate the annotation Slide from Jim Martin 10
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6/1/11 ML Approach Slide from Jim Martin 11
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6/1/11 Encoding for Sequence Labeling We can use IOB encoding: United Airlines said Friday it has increased B_ORG I_ORG O O O O O the move , spokesman Tim Wagner said.
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124.11.lec7 - CS 124/LINGUIST 180 From Click to edit Master...

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