Recall that our features φ(s, a) for both pruning and scoring functions are defined over state-action pairs, where each state s consists of a set of clusters and an action a corresponds to merging an unprocessed mention m with a cluster C in state s or create one for itself.
coreference resolution is a structured prediction problem where the set of mentions m 1 , m 2 , • • • , m D extracted from a document cor-reponds to a structured input x and the structured output y corresponds to a partition of the mentions into a set of clusters c 1 , c 2 , • • • , c k .