Consistency of UML class diagrams with hierarchy constraints

UML class diagrams are probably the most important, well-established, UML model. They play an essential role in the analysis and design of complex systems. UML class diagrams allow the specification of constraints such as cardinality. constraints, class hierarchy constraints and inter-association constraints. Constraints extend the expressivity of class diagrams, but enable the specification of unsatifiable class diagrams, i.e., class diagrams that have no finite non-empty instance world. Nowadays, UML case tools still do not check satisfiability of class diagrams, and implementation languages still do not enforce design level constraints. But the expectation is that in the future, and in particular with the prevalence of the Model Driven Engineering approach,all information in a design model will be effective in its successive models.