  In response to the need to design this declarative component, a subfield of AI known as knowledge representation emerged during the 1980s. Knowledge representation deals primarily with the representational and reasoning challenges of this separate component. The best place to get a feel for this subject is the proceedings of the meetings that are now held every other year: see  Brachman et al. 1989,  Allen et al. 1991,  Nebel et al. 1992,  Doyle et al. 1994,  Aiello et al. 1996,  Cohn et al. 1998,  Cohn et al. 2000,  Fensel et al. 2002,  Dubois et al. 2004,  Doherty et al. 2006,  Brewka &amp; Lang 2008,  Lin et al. 2010,  Eiter et al. 2012,  Baral et al. 2012,  and  Baral et al. 2016.