Life-Cycle Inheritance: A Petri-Net-Based Approach

Inheritance is one of the key issues of object-orientation. The inheritance mechanism allows for the definition of a subclass which inherits the features of a specific superclass. This means that methods and attributes defined for the superclass, are also available for objects of the subclass. Existing methods for object-oriented modeling and design, abstract from the dynamic behavior of objects when defining inheritance. Nevertheless, it would be useful to have a mechanism which allows for the inheritance of dynamic behavior. This paper describes a Petrinet-based approach to the formal specification and verification of this type of inheritance. We use Petri nets to specify the dynamics of an object class. The Petri-net formalism allows for a graphical representation of the life cycle of objects which belong to a specific object class. Four possible inheritance relations are defined. These inheritance relations can be verified automatically. Moreover, four powerful transformation rules which preserve specific inheritance relations are given.