A Symmetric Nets Emulator for Adaptive P/T Nets

摘要

Despite Petri Nets represent a sound and expressive formal model for distributed discrete-event systems, they cannot specify in a natural way structural changes caused by adaptation procedures that are likely to occur in distributed applications running in a dynamically changing environment. In this paper a framework based on the Symmetric Nets formalism (SN) is proposed, able to emulate the behaviour of any Place/Transition (P/T) system, and safely implement changes to system's layout during execution. The advantage of this proposal is twofold: (i) the intrinsic features of SN formalism (and its timed extension) for efficient (performance) analysis can be exploited, (ii) powerful off-the-shelf software tools, that natively support Symmetric Nets, can ease both the modelling and the analysis phases. The limited data abstraction capabilities of SN require the use of a highnumber of non observable transitions to simulate the atomic firing of Petri nets' transitions. This gives rise to complexity issues in the model analysis, that are thoroughly discussed and (partially) faced.