Two Theses of Knowledge Representation - Language Restrictions, . . . They also separate terminological and assertional knowledge, and restrict classification to purely terminological information.
Horn clauses, where each clause is a disjunction of literals, at most one of which is positive.
Doc 34 Massachusetts Institute of Technology - Smith, semantics et al. Doc 1 Taxonomic syntax for first order logic - McAllester, Givan et al. Moore, summary et al. The graph only includes citing articles where the year of publication is known.