The notion of uniform closure operator is introduced, and it is shown how this concept surfaces in two di erent areas of application of abstract interpretation, notably in semantics design for logic programs and in the theory of abstract domain re nements. In logic programming, uniform closures permit to generalize, from an order-theoretic perspective, the standard hierarchy of declarative semantics. In particular, we show how to reconstruct the modeltheoretic characterization of the well-known s-semantics using pure order-theoretic concepts only. As far as the systematic re nement operators on abstract domains are concerned, we show that uniform closures capture precisely the property of a re nement of being invertible, namely of admitting a related operator that simpli es as much as possible a given abstract domain of input for that re nement. Exploiting the same argument used to reconstruct the ssemantics of logic programming, we yield a precise relationship between re nements and their inverse operators: we demonstrate that they form an adjunction with respect to a conveniently modi ed complete order among abstract domains.