On the Design of Behavior Consistent Specialization of Object Life Cycles in ODB and UML

Object-oriented design methods express the behavior an object exhibits over time, i.e., the object life cycle, by notations based on Petri nets or statecharts. This chapter investigates and compares the specialization of object life cycles in type hierarchies for two design notations: Object Behavior Diagrams (OBD), which have been originally developed for object-oriented database design and are based on Petri nets, and the Unified Modeling Language (UML), which is based on statecharts. This work treats specialization as a combination of extension and refinement. It uses the notions of observation consistency and invocation consistency to compare the behavior of object life cycles. It presents necessary and sufficient rules to check for behavior consistency in the realm of OBD and outlines how these rules may be applied to UML. Whereas specialization can always be strictly split into an extension part and a refinement part in OBD, the concurrency restrictions of UML sometimes require using what is technically a refinement in order to represent an intended parallel extension.