Hence, to jointly learn discourse-new detection and coreference resolution, we must train the ranker using instances generated from both discourse-old and discourse-new mentions.
when training the ranker, we provide each active mention with the option to start a new cluster by creating an additional instance that (1) contains features that solely describe the active mention (i.e., the features shown in the second block of Table 1), and (2) has the highest rank value among competing clusters (i.e., 2) if it is discourse-new and the lowest rank value (i.e., 1) otherwise.