Discriminative methods such as Conditional Random Fields (CRFs) (Lafferty et al., 2001), Semi-Markov Random Fields (Sarawagi and Cohen, 2004), and perceptrons (Collins, 2002a) have been popular approaches for sequence labeling because of their excellent performance, which is mainly due to their ability to incorporate many kinds of overlapping and non-independent features.
note that if the features are all local, the secondbest candidate (generally n-best candidates) can also be found efficiently by using an A* search that uses the best scores calculated during a Viterbi search as the heuristic estimation (Soong and Huang, 1991).