A new notion in Petri nets is introduced: the ‘Minimal Preconservative Components’ (CPCM), that reinforces the links between a Petri net and its graph G=(P,T;¦)’+,V) and provides an original tool in order to deduce from the very structure of the net and without considering the marketings, important behaviour properties. A CPCM is a non empty set of places, I, minimal of solution of ¦)’+(I)=¦)’-(I). The authors first prove several basic properties of any CPCM. Next, they propose three types of reductions that allow, on one hand, to introduce further properties of any CPCM and, on the other hand, to limitate the combinatorial aspect of the CPCM determination. For most examples that modelize real life systems, the only application of these reductions provides the set of all CPCM otherwise, the authors propose a Boolean algorithm for finding the CPCM of the reduced net and a labelling process that allows to deduce the CPCM of the initial net.
