Hypernets: a class of hierarchical petri nets

The interest of this thesis is on modeling systems of mobile agents, systems composed of several open and autonomous components which can interact and move inside one or more environments. Several proposal for modeling mobility have been introduced. They can be roughly divided in two categories: Petri net based formalisms, and process algebra based formalisms. In this thesis, Petri net formalisms will mostly be considered, with particular care to formalisms which use the nets-within-nets paradigm. In models compliant to this paradigm the tokens of a Petri net can be nets themselves. Since systems of mobile agents exhibit a nesting structure, it seems natural to use this paradigm. In particular, the focus of this dissertation is on the hypernet model, whose main characteristic is that it has a limited state space, characteristic that make it suitable to be analyzed using well known Petri net techniques. The thesis topics range from theoretical aspects of the model to more practical issues. From a theoretical point of view an extension of the model is introduced. It is proved that this extension preserves all the good properties of the basic model. It is also studied how to apply the well known unfolding technique to this model. From a practical point of view is is shown how the nets-within nets paradigm can be used to model systems based on the Grid infrastructure. Moreover, a tool which allow to draw and to analyze an hypernet is discussed.