Leroux has proved that unreachability in Petri nets can be witnessed by a Presburger separator. i. e. if a marking $\vec{m}_\text{src}$ cannot reach a marking $\vec{m}_\text{tgt}$. https://www.spidertattooz.com/The-GelBottle-Inc-BIAB-Gel-Polish-Spirited-67oz-p17706/