The resultant labels are then used together with word length, existence of special characters in the word, current, previous and next words to train a CRF model that predicts the token level classes of words in a given sentence/tweet.
for within language varieties, AIDA (Elfardy et al., 2014) and AIDA2 (Al-Badrashiny et al., 2015) are the best published systems attacking this problem in Arabic.