In: Proceedings of the Third Annual Symposium on Logic in Computer Science, pages 155-164. IEEE Comput. Soc. Press, Washington, DC, USA, 1988.
Abstract: The composition and extraction mechanisms of Petri nets are at present inadequate. This problem is solved by viewing place/transition Petri nets as ordinary, directed graphs equipped with two algebraic operations corresponding to parallel and sequential composition of transitions. A distributive law between the two operations captures a basic fact about concurrency.