Let λ be a parameter vector and f (y s−1 , y s , x) be a (local) feature vector obtained from the corresponding position s given x. CRFs define the conditional probability, p(y|x), as being proportional to a product of potential functions on the cliques.
with respect to the performance of NER and Chunking tasks, the current best performance is reported in (Ando and Zhang, 2005), which we refer to as 'ASO-semi', as shown in Figures 5 and 6.