Example summaries for DUC’04 produced by RL (see Section 5.4) with a reward function learnt from 100 user interactions using (a) the BT, UNC method of Gao et al. (2018) and (b) our GPPL, IMP method. (c) is a model summary written by an expert. Each color indicates a particular news event or topic, showing where it occurs in each summary. Compared to (a), summary (b) covers more of the events discussed in the reference, (c).