Open-vocabulary LM

[Amélie DELTOUR]

Hi,
Is it normal that in an open-vocabulary LM (built with the "-unk" 
option) the <unk> token is present as unigram, but not in bigrams and 
trigrams?
(Sorry if this is a silly question, but I am not so familiar with 
language models, and I was told that it would not be the case with other 
toolkits).
Thanks again,

Amélie

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Amélie DELTOUR
ENSIMAG / Universität Karlsruhe
E-mail : amelie.deltour at ira.uka.de
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