Much recent effort has been put into building Knowledge Bases (KBs), either manually curated (Freebase (Bollacker et al., 2008), Cyc (Lenat, 1995)) or automatically produced (YAGO (Suchanek et al., 2007), Knowledge Vault (Dong et al., 2014)), ranging from logically consistent linked-data in OWL (SUMO (Pease et al., 2002)) to little-structured sets of textual relations extracted from text (NELL (Mitchell et al., 2015)) with Open IE systems (Reverb, Ollie (Mausam et al., 2012), ClausIE (Del Corro and Gemulla, 2013), Stanford Open IE (Angeli et al., 2015), CSD-IE (Bast and Haussmann, 2013)).
large they may be, typical KBs are largely incomplete, and many relevant facts are missing (West et al., 2014).