This modest improvement indicates value in optimising the rare word threshold.
unknown Handling Results we were able to increase part-of-speech tagging performance in three ways: by adapting the idea of normalisation and implementing it with both fixed word-lists (repairing all but 20% of problem tokens), with extra features encoding word shapes to handle OOV terms, and with a  Table 7: Impact of prior labeling and mapping slang to IV terms on T-dev; rare word threshold is 3. more sensitive threshold to inclusion of rare words in the model.