“…Most of these systems implement (extended versions of) the resolution principle introduced by Lee [19], such as Elf-Prolog [10], F-Prolog [20], generalized annotated logic programming [17], Fril [4], MALP [24], R-fuzzy [9], the QLP scheme of [31] and the many-valued logic programming language of [36,34]. There exists also a family of fuzzy languages based on sophisticated unification methods [33] which cope with similarity/proximity relations, as occurs with Likelog [3], SQLP [8], Bousi∼Prolog [16,32] and FASILL [14,15]. Some related approaches based on probabilistic logic programming can be found, e.g., in [29,7].…”