Publication Date




To appear in International Journal of Intelligent Systems.


There are two main fuzzy system methodologies for translating expert rules into a logical formula: In Mamdani's methodology, we get a DNF formula (disjunction of conjunctions), and in a methodology which uses logical implications, we get, in effect, a CNF formula (conjunction of disjunctions). For both methodologies, universal approximation results have been proven which produce, for each approximated function f(x), two different approximating relations RDNF(x,y) and RCNF(x,y). Since in fuzzy logic, there is a known relation FCNF(x)<=FDNF(x) between CNF and DNF forms of a propositional formula F, it is reasonable to expect that we would be able to prove the existence of approximations for which a similar relation RCNF(x,y)<=RDNF(x,y) holds. Such existence is proved in our paper.