The output layer employs a conditional random field (CRF) to infer the POS t i of each word w i based on the feature layer outputs.
the conditional probability of a tag sequence given an input sentence is: where Z(⃗ x) is the partition function: the output clique potential Ψ(⃗ x, ⃗ y i ) shows the correlation between inputs and output labels: Ψ(⃗ x, ⃗ y i ) = exp(⃗ s i ), with the emission vector ⃗ s i being defined as: where ⃗ θ 0 is the model parameter.