We introduce an object-oriented approach to transform a star-schema of a legacy data warehouse system into a Dimensional Object Model (DOM) (Firestone, 2000), in order to take advantage of the flexibility of the object paradigm. We have applied the Object-Oriented Software Engineering (OOSE) process, proposed by (Jacobson et al., 1992), to describe the life cycle of a data warehouse and to clarify the context of our intervention. By means of OOSE we also define the target architecture and the components that will ensure the development of reuse-supporting data warehouse systems. In a sense, a change tolerant architecture is proposed, as referred to by (Jacobson, 2000). The solution proposed applies the object paradigm for the star-schema decomposition in a three-layer architecture, separating the components in logical, interface and data management layers. This decomposition minimizes the dependence among the components and increases their reusability. The main contribution of this work is that, by transforming the star-schema into a DOM, we are preparing the system to evolve through any object-oriented data warehouse development methodology. In a context of many already existing data warehouse systems based on relational models, this transformation sounds especially interesting.