We study mechanism design in quasi-linear environments when there are two alternatives. We show that under a mild range condition, every implementable deterministic allocation rule is a generalized utility function maximizer. In unbounded domains, if we replace our range condition by an...

We provide axiomatic characterizations of two natural families of rules for aggregating equivalence relations: the family of join aggregators and the family of meet aggregators. The central conditions in these characterizations are two separability axioms. Disjunctive separability, neutrality,...