The star model, broadly used in data warehouse modeling, is a logical model, so its representation is strongly dependent on the database technology used for its implementation, usually relational. The method recommended for designing a dimensional system would be the use of a conceptual model, for which UML has become a standard, and the application of a technique for mapping such OO Conceptual Model into a Relational Logical Model. This article presents the advantages of using the denormalization technique (here called dimensional) instead of the traditional techniques (used for mapping OO OLTP systems into Relational) for transforming OO dimensional models (especially the extended ones) from its conceptual to a logical phase