Handling Mutual Exclusion in UML Class Diagrams

UML is a standard modelling language that is able to specify a wide range of object-oriented concepts. However, there are some aspects that UML does not fully discuss. For example, UML has no mechanism to prevent the specification, for semantic reasons, of undesirable relationships. With the fast evolution of the requirements of our nowadays applications we cannot simply rely on omitting what we do not want to happen. We explicitly have to specify unwanted concepts. We are referring to the concept of mutually excluding classes. Moreover, the lack of formalisation compromises the precision of the specification of the concepts. By using formal description techniques, such as Object-Z, we can reason about the requirements and identify ambiguities and inconsistencies earlier in the development process. Particularly, the formal specification can be used through the software evolution. In general, we can say that formalising helps obtaining a more reliable system. Our aim is to specify precisely mutually excluding classes.