On the one hand, systems like LTG (Mikheev et al., 1998), MUSE (Maynard et al., 2001), HNERC (Farmakiotou et al., 2002), OAK (Sekine and Nobata, 2004), (Magnini et al., 2002) and (Arora et al., 2009) use pattern-based rules.
it is worth mentioning approaches based on Hidden Markov Model (HMM) like Nymble (Bikel et al., 1997) and (Zhou and Su, 2002).