Partial order behaviour and structure of Petri Nets

This paper argues that partial order semantics can be used profitably in the proofs of some nontrivial results in Petri net theory. We show that most of Commoner's and Hack's structure theory of free choice nets can be phrased and proved in terms of partial order behaviour. The new proofs are considerably shorter (and, arguably, more lucid) than the old ones; they also generalise the results from (safe) free choice nets to (bounded) extended free choice nets.