02.04.2013 Views

Perplexity of n-gram and dependency language models

Perplexity of n-gram and dependency language models

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Language Models – design decisions<br />

1) How to factorize P(w1, w2, ... wm) into Πi=1..m P(wi | hi), this<br />

i.e. what word-positions will be used as the context hi ?<br />

work<br />

2) What additional context information will be used<br />

(apart from word forms),<br />

e.g. stems, lemmata, POS tags, word classes,... ?<br />

3) How to estimate P(w i | h i ) from the training data?<br />

Which Linear smoothing interpolation technique will be used?<br />

Weights (Good-Turing, trained Jelinek-Mercer, by EM<br />

Katz, Kneser-Ney,...)<br />

Generalized Parallel Back<strong>of</strong>f etc.<br />

14

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