Object-oriented (OO) modeling and design methodologies have been receiving a significant attention since they allow a quick and easy-to-gasp overview about a complex model. However, in the literature there are no formal frameworks that allow designers to verify the consistency (absence of contradictions) of both the static and dynamic components of the specified models, that are often assumed to be consistent. In this paper, a unifying formal framework is proposed that allows the consistency checking of both the static and dynamic components of a simplified OO model.