Behaviour specification of active objects in open generative communication environments

Coordination models based on generative communication are well established for modelling interactions between agents in open systems. Because such models focus on shared data spaces and not on the active agents operating on them, they lack adequate modelling power for specifying agent behaviour. Our work is based on the Objective Linda coordination model (Kielman, 1996) which exploits generative communication and object-based modelling in order to meet the requirements of open systems. For Objective Linda, we present a high-level Petri net formalism for agent behaviour specification that combines an easily understandable, visual representation with the applicability of formal reasoning on agent behaviour. Based on this formalism, we introduce a notion of types and subtyping for active agents. We illustrate the benefits of our work on an example from open systems design