In: Petri Net Newsletter Vol. 64, April 2003, Special Event: Advanced Course on Petri Nets, Eichstätt, Sept. 15-26, 2003, Gesellschaft für Informatik e.V., pages 7-14. 2003.
Abstract: Two central types of problems in combinatorics are those of counting and classifying discrete objects (where problems of the latter type are harder as objects are counted as a by-product in a classification). For many interesting types of objects, including Petri nets, neither explicit nor recursive formulas for the number of objects with given parameters are known. In this study, we consider the class of Petri nets that can be viewed as strongly connected bicolored digraphs, and present an approach for classifying such graphs utilizing the graph isomorphism program nauty. The number f Petri nets for small parameters is tabulated.