A theoretical approach to determine innovative evaluation of model quality is proposed. This approach is based on two different mappings to design the same conceptual database model: the former is a vertical mapping composed of bottom-up steps. It starts from the specification of a database applications supported by a formal model and achieves a resulting model based on semantic data models. The latter is a horizontal mapping composed of successive model extensions. It starts from a graph of conceptual classes and achieves the resulting model of the previous mapping. Formulas for the quantitative/numerical evaluations of the models are introduced during the vertical mapping, whereas “formulas” for the qualitative/conceptual evaluations of models are introduced during the horizontal mapping. The quantitative evaluations express the costs of what has been specified/proven in terms of variable and constant cardinality. The qualitative/conceptual evaluations express the saving that you get for what has been implicitly specified/proved. The quality measure of the resulting model is given in terms of hidden classes. These provide indication about different aspects of the model quality.