Sets are pairwise-disjoint if and only if every set is disjoint from every other set.
(<=> (Pairwise-Disjoint @Sets) (Forall (?S1 ?S2) (=> (Item ?S1 (Listof @Sets)) (Item ?S2 (Listof @Sets)) (Or (= ?S1 ?S2) (Disjoint ?S1 ?S2)))))
(Forall (?S1 ?S2) (=> (Item ?S1 (Listof @Sets)) (Item ?S2 (Listof @Sets)) (Or (= ?S1 ?S2) (Disjoint ?S1 ?S2)))) (Undefined (Arity Pairwise-Disjoint))
(Instance-Of (Arity Pairwise-Disjoint) Undefined) (<=> (Pairwise-Disjoint @Sets) (Forall (?S1 ?S2) (=> (Item ?S1 (Listof @Sets)) (Item ?S2 (Listof @Sets)) (Or (= ?S1 ?S2) (Disjoint ?S1 ?S2))))) (<=> (Set-Partition ?S @Sets) (And (= ?S (Union @Sets)) (Pairwise-Disjoint @Sets)))