The OCL 1.4 specification introduces let-declarations for adding auxiliary class features in static structures of the UML. We provide a type inference system and a big-step operational semantics for the OCL 1.4 that treat UML static structures and UML object models abstractly and accommodate for additional declarations; the operational semantics satisfies a subject reduction property with respect to the type inference system. We also discuss an alternative, non-operational interpretation of let-declarations as constraints.