High Quality Content by WIKIPEDIA articles! Petri Net Markup Language (PNML) is an interchange format aimed at enabling Petri net tools to exchange Petri net models. PNML is an XML-based syntax for high-level Petri nets, which is being designed as a standard interchange format for Petri net tools. It will end up being the second part of the ISO standard ISO/IEC 15909. PNML grammar is publicly available on its reference site.