Algorithms for NLP IITP, Spring 2020 HMMs, POS tagging, NER Yulia - - PowerPoint PPT Presentation

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Algorithms for NLP IITP, Spring 2020 HMMs, POS tagging, NER Yulia - - PowerPoint PPT Presentation

Algorithms for NLP IITP, Spring 2020 HMMs, POS tagging, NER Yulia Tsvetkov 1 Plan POS tagging recap HMMs, Viterbi HMMs+ dealing with UNKs 3gram HMMs multilingual POS tagging Featurizing HMMs MEMM,


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Yulia Tsvetkov

Algorithms for NLP

IITP, Spring 2020

HMMs, POS tagging, NER

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▪ POS tagging recap ▪ HMMs, Viterbi ▪ HMMs+

▪ dealing with UNKs ▪ 3gram HMMs ▪ multilingual POS tagging

▪ Featurizing HMMs

▪ MEMM, CRF

▪ NER ▪ HMMs is speech recognition

Plan

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https://universaldependencies.org

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▪ → →

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Levels of linguistic knowledge

Slide credit: Noah Smith

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▪ map a sequence of words to a sequence of labels ▪ Part-of-speech tagging (Church, 1988; Brants, 2000) ▪ Named entity recognition (Bikel et al., 1999) ▪ Text chunking and shallow parsing (Ramshaw and Marcus, 1995) ▪ Word alignment of parallel text (Vogel et al., 1996) ▪ Compression (Conroy and O’Leary, 2001) ▪ Acoustic models, discourse segmentation, etc.

Sequence Labeling

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Sequence labeling as classification

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the future is independent of the past given the present

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the future is independent of the past given the present

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  • 1
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  • n

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...

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▪ ▪ ▪

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▪ → ▪ → ▪ → ▪ → ▪ → ▪ →

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ssssssssppppeeeeeeetshshshshllllaeaeaebbbbb “speech lab”

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