Constraints in generalization structures in conceptual database schemes

We introduce two types of constraints on generalization structures in conceptual database schemes: non exclusive cardinality and non exhaustive cardinality constraints. We present some of the problems to express these constraints in Batini's EER model (C. Batini et al., 1994), and we explain how the expansion of this model through the addition of new new constraints generating rules may enhance the scheme legibility and expressiveness.