The Evolving Algebra Semantics of Class and Role Hierarchies

The formal description of the semantics of object-oriented data models is still a heavily debated research problem. This paper shows how evolving algebras provide an elegant way to specify the operational semantics of object-oriented data models. In particular, we define the formal semantics of a novice feature of object-oriented data models proposed recently by different authors: role hierarchies. As opposed to traditional class hierarchies, role hierarchies allow objects to dynamically acquire multiple independent types.