Combining deterministic and stochastic Petri net and product-form queueing network models for evaluating gracefully degradable systems

An approach is introduced for determining the performability of repairable degradable systems based on combining deterministic and stochastic Petri nets and product-form queuing network models. The novel feature of the proposed modeling technique lies in its detailed representation of the transient behavior during a reconfiguration process. The reconfiguration time of a task and the rebooting time of a processor are represented in the model as deterministic delays. A hierarchical decomposition method is used in order to reduce the computational effort of the solution. The employment of this decomposition technique leads to an exact solution because there is no interaction between a flow-equivalent transition and the complementary subnet of the aggregated DSPN (deterministic and stochastic Petri nets)