Bericht FBI-HH-B-185/96, Fachbereich Informatik, Universität Hamburg, 45 pp. pages, 1996.
Abstract: Objects are studied as higher-level net tokens having an individual dynamical behaviour. In the context of Petri net research it is quite natural to model such tokens also by Petri nets. To distinguish them from the system net, they are called object nets. Object nets behave like tokens, i.e., they are lying in places and are moved by transitions. In contrast to ordinary tokens, however, they may change their state (i.e. their marking) when lying in a place or when being moved by a transition. By this approach a pretentious and challenging two-level system modelling technique is introduced. Similar to object-oriented programming, complex systems are modelled close to their real appearance in a natural way to promote clear and reliable concepts. Applications in fields like workflow, agent-oriented programming (as in AI research) or open systems networks are feasible. This report gives, for the first time, a precise definition of the basic model together with a suitable process semantics. Different but equivalent notions of such processes are studied as well as some of their elementary properties. To outline further research on n-level models, a 3-level object system is discussed.
Keywords: higher-level net model; causality/partial order theory of concurrency; system design using nets; object nets; processes; elementary net systems; interleaving and partial order process semantics.