Have you tried ontological based text coding to classify and generate featured vectors??

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CRF feature construction is an open problem and the solution relies heavily on expert domain knowledge (and quite a bit of patience !)

for a starter, see

http://blog.echen.me/2012/01/03/introduction-to-conditional-random-fields/

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for a proposal of automatic feature construction, see

http://arxiv.org/ftp/arxiv/papers/1212/1212.2504.pdf

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