Actions of Boolean rings on sets

LetB be a Boolean ring (with 1),S a sheaf of sets on the Stone space Spec(B), andS the set of global sections of S. For everya B ands, t S, leta(s, t) denote the element ofS which agrees withs on the support ofa, and witht elsewhere.We set down identities satisfied by this ternary operationB×S×SS (involving also the Boolean operations ofB). For a fixed Boolean ringB, we call a setS given with a ternary operation satisfying these identities aBset. The above construction is shown to give a functorial equivalence between sheaves of setsS on Spec(B) with nonempty sets of global sections, and nonemptyB-setsS. For any setA, the bounded Boolean powerA[B]^* is the freeB-set onA. The varieties ofB-sets, asB ranges over all Boolean rings, constitute (together with one trivial variety) the least nontrivial hypervariety of algebras, in the sense of W. Taylor.This work was done while the author was partly supported by NSF contract DMS 85-02330.Presented by R. S. Pierce.