Soundness of Workflow Nets with Reset Arcs is Undecidable !

Petri nets are often used to model and analyze workflows. Many workflow languages have been mapped onto Petri nets in order to provide formal semantics or to verify correctness properties. Typically, the so-called Workflow nets are used to model and analyze workflows and variants of the classical soundness property are used as a correctness notion. Since many workflow languages have cancelation features, a mapping to workflow nets is not always possible. Therefore, it is interesting to consider workflow nets with reset arcs. Unfortunately, soundness is undecidable for workflow nets with reset arcs. In this paper, we provide a proof and insights into the theoretical limits of workflow verification.