The main purpose of this paper is to give a method for
construction of the reduced reachability graph for Stochastic Petri Nets
(SPN), the symbolic graph. This construction is achieved by exploiting
the structural symetries in the net using the theory of bisimulation of
places for detecting isomorphic parts in the net. The symbolic graph,
being isomorphic to an agregated Markov chain, may be used to prove
qualitative properties as liveness, boundness, ... Moreover, this
reduced graph make more easy the computation of the performance measures
of interest as the mean number of tokens in a place, the mean number of
firing transition ... We have so developped a tool, SSPN (Stochastic
Symetric Petri nets), for generating the symbolic graph and deducing
qualitatives and quantitatives properties.