Cardinality constraints as well as key constraints and functional dependencies are among the most popular classes of constraints in database models. While each constraint class is now well understood, little is done about their interaction. Today cardinality constraints and key constraints are embedded in most CASE tools, which are usually based on the Entity-Relationship model. However, these tools do not offer intelligent consistency checking routines for cardinality constraints. They do not consider the global coherence of them. Conflicts among the constraints are not detected. Our aim is then, to propose a tool for reasoning about a set of cardinality constraints, key and certain functional dependencies in order to help in database design. We will treat the global coherence of cardinality constraints. We propose two steps: a syntactical analysis according to our ER Meta-schema and a semantic analysis in order to verify the cardinality constraints and their interactions.