[Ligncse256] POSTagger Trigrams

[Andrea Biaggi]

I have a question how to handle trigrams for P(t_i|t_{i-1}t_{i-2}).
It is always the case that this probability is >0 for every combinations 
of tags in the validation/test set using counts of the trigram in the 
training set?
Or we have to use a backoff/interpolation schema to handle all the 
possible cases? Or use some other techniques? Or just saying that it is 
= 0, therefore not a possible combination?

-- 
Andrea Biaggi abiaggi at cs.ucsd.edu