For exam-ple, the ICSI system (Gillick et al., 2008) removed the sentences that are too short or have non-overlap with the queries, and concepts with document frequency less than 3, resulting in 95.8 sentences and about 80 concepts per topic on the TAC2009 dataset.
the actual scale of ILP is rather small after pruning (e.g., 176 variables and 372 constraints per topic).