Stochastic well formed colored nets (SWN) make it possible to apply performance evaluation techniques on a compact representation of the reachability graph (RG), called the Symbolic RG (SRG). The Extended SRG (ESRG) has been proposed to achieve a higher degree of reduction when applied to partially symmetric SWN models. The price to pay for the more effective state space reduction, is a loss of information on the paths of the graph. Despite this loss, it has been shown that several qualitative properties can be studied on the ESRG. We consider the possibility of using the ESRG for performance evaluation purposes and more specifically, we explore how the ergodicity of the system can be decided on this graph.

The class of stochastic well-formed colored nets (SWN's) was defined as a syntactic restriction of stochastic high-level nets. The interest of the introduction of restrictions in the model definition is the possibility of exploiting the symbolic reachability graph (SRG) to reduce the complexity of Markovian performance evaluation with respect to classical Petri net techniques. It turns out that SWN's allow the representation of any color function in a structured form, so that any unconstrained high-level net can be transformed into a well-formed net. Moreover, most constructs useful for the modeling of distributed computer systems and architectures directly match the "well-formed" restriction, without any need of transformation. A nontrivial example of the usefulness of the technique in the performance modeling and evaluation of multiprocessor architectures is included.>