Modelling and verification of ambient systems using petri nets

Abstract

The expeditious development of technology in the past decades re- sulted in the introduction of concurrent systems that incorporate both ubiquitous and pervasive computing, the ambient systems. These sys- tems are named after their ability to be completely embedded in the environment in which they operate and interact with the users, in a silent and non distracting way, facilitating the completion of their tasks. Hence, there is a growing need to introduce and develop formal tech- niques for computational models capable of faithfully modelling the behaviour of these systems. One way of capturing the intricate be- haviours of the ambient systems is to use Petri nets, which are a modelling language that is used for the representation and analysis of concurrent systems. Within the domain of rigorous system design, veri cation of systems e ectively checks and guarantees the correctness of the examined mod- els with respect to the speci cation. This work investigates the modelling and the analysis of ambient sys- tems using Petri nets. To examine the modelling of these systems, their taxonomy into Ambient Guidance Systems and Ambient Infor- mation Systems is carried out and a case study is used for the mod- elling of each category. To model ambient systems, the step-modelling approach and a vari- ant class of Coloured Petri Nets, the Ambient Petri Nets (APNs), are introduced. Step modelling approach focuses on the interaction be- tween the system and the user and Ambient Petri Nets is a class of nets with colour-sensitive inhibitor arcs that is used especially for the structural and behavioural representation of ambient systems. For the modelling of general ambient systems, the compositionality of the Ambient Petri Nets is used. To verify the correctness of the produced Ambient Petri Nets models, the introduction of the Transformed Ambient Petri Nets class that has no colour-sensitive inhibitor arcs is required since Charlie and generally most of the existing veri cation tools do not support the analysis of inhibitor nets. To address this problem, a construction is de ned to translate the Ambient Petri Nets into Transformed Ambient Petri Nets. Afterwards, the Step Transition Systems are used to prove the behavioural equivalence of the nets that are associated through the construction. Subsequently, the Transformed Ambient Petri Nets models of the cho- sen case studies are veri ed against model checking and qualitative properties. For the rst category, Computation Tree Logic (CTL) is used to check the models against important properties of the ambient systems that are related to their features and their general function- ing. Finally, qualitative properties consider fundamental structural and behavioural properties of Petri nets that provide useful outcome about the systems under consideration.