UML 2 has improved the expressiveness of the language with respect to associations in several manners. A significant one has been the introduction of the association redefinition concept. Association subsetting and association specialization have been included in UML since its earliest versions and share some relevant features with association redefinition. These similarities among the three constructs make it frequently difficult, especially to novice users, to: decide which one of these concepts is the best suited to model a particular situation; systematically justify their modelling choices. In this report, we present a preliminary empirical investigation on these constructs using as a benchmark a catalogue of model examples produced by different authors which can be considered experts in the conceptual modelling field.