First-order, constrained, linear-chain conditional random fields.
The library provides efficient implementation of the first-order, linear-chain conditional random fields (CRFs) with position-wise constraints imposed over label values.
It is strongly related to the simpler http://hackage.haskell.org/package/crf-chain1 library where constraints are not taken into account and all features which are not included in the CRF model are considered to have probability of 0. Here, on the other hand, such features do not influence the overall probability of the (sentence, labels) pair - they are assigned the default potential of 0.
Efficient algorithm for determining marginal probabilities of individual labels is provided. The tagging is performed with respect to marginal probabilities.