The vast majority of previous work (Wan et al., 2007;Wan, 2008;Wan and Xiao, 2009;Wan and Zhang, 2014) creates summaries by ranking textual segments (usually sentences) according to their relationship (e.g., similarity) to other segments and their relevance to the query.
relevance and evidence estimation are subservient to estimating the centrality of a segment (e.g., with a graph-based model).