Data encapsulation and date abstraction with petri nets : A graphical visualization of modules

In this paper, the concepts of data encapsulation and data abstraction are applied to Petri nets. Encapsulation is realized by enclosing a data object inside a high level Petri net. Access to the data object is permitted only via exported operations. Abstraction is realized by separating a definition net and an implementation net. This separation is a well known concept of modules, used to handle the complexity problem of large systems and to increase the reusability and maintainability. But this concept has not yet been applied to a modelling technique with Petri nets. Two new hierarchy concepts are introduced to establish the connection between the implementation net and the definition net of one module and between different modules, respectively. Together with the new methodical concepts, a graphical notation of the Petri net model is introduced, which results in an intuitive visualization of Petri net modules.