Exploration of coreference resolution: The ACE entity detection and recognition task

In this paper, we consider the coreference resolution problem in the context of information extraction as envisioned by the DARPA Automatic Content Extraction (ACE) program. Given a set of entity mentions referring to real world entities and a similarity matrix that characterizes how similar those mentions are, we seek a set of entities that are uniquely co-referred to by those entity mentions. The quality of the clustering of entity mentions into unique entities significantly depends on the quality of (1) the similarity matrix and (2) the clustering algorithm. We explore the coreference resolution problem along those two dimensions and clearly show the tradeoff among several ways of learning similarity matrix and using it while performing clustering.