Prototypes can be an effective way of interacting with an end-user to validate that the user's requirements have been correctly captured. In the formal methods community, specification animation has been investigated as a way of creating a kind of prototype that is generated from a formal specification. Enriching UML diagrams with OCL constraints can provide the formality that is needed to animate the diagrams without the need for a more rigorous formal specification language. This paper provides an overview of issues concerning specification animation and describes an initial attempt at an animation environment for UML/OCL. We translate the UML/OCL into an object-oriented declarative language, Prolog++, and utilize a primitive animation environment that allows both a developer and client to explore the validity of the specification. In particular, in this paper we focus on animating the effect of constraints.