Object Oriented Modeling with Object Petri Nets

This paper informally introduces Object Petri Nets (OPNs) with a number of examples. OPNs support a thorough integration of object-oriented concepts into Petri Nets, including inheritance and the associated polymorphism and dynamic binding. They have a single class hierarchy which includes both token types and subnet types, thereby allowing multiple levels of activity in the net. The paper discusses some theoretical issues pertinent to the definition of OPNs, and compares the provisions of OPNs with those of other Concurrent Object-Oriented Programming Languages. The paper then considers a case study of using OPNs to model a cooperative editor for hierarchical diagrams. This extended example demonstrates the applicability of OPNs to the modelling of non-trivial concurrent systems. The methodology for deriving a Petri Net model is to adapt an object-oriented design methodology: the Object Model is prepared in Rumbaugh’s OMT notation; the Dynamic Model is then prepared in the form of lifecycles, following the Shlaer-Mellor methodology; and finally these models are mapped into an OPN model. This approach has the advantage of guiding the development with well-accepted methodologies, and demonstrates the generality and flexibility of the OPN formalism.