In: Burkhard, H.-D.; Czaja, L.; Nguyen, H.-S.; Starke, P.: Proceedings of the CSP'99 Workshop, Warsaw, 28-30 September 1999, pages 24-35. 1999.
Abstract: The problem of completeness of categories of Petri nets is studied. Since general Petri nets have products, the problem reduces to the issue of the existence of equalizers. We show that the general category of Petri nets has no equalizers, and hence it is not complete. On the other hand, its full subcategories of reachable safe nets is complete.