In 2000, there was a workshop [1] that should foster the definition of a standard transfer format for Petri nets as a satellite event of the annual ‘Petri Net Conference’ in Aarhus. As a result of this first workshop, after many other discussions and meetings, the Petri Net Markup Language (PNML) is about to be finally adopted as ISO/IEC 15909-2. Over the years, PNML has evolved and, unfortunately, there are many different intermediate versions and variants, that are still in use. With this paper, we would like to report on the final result and on PNML as it is defined in ISO/IEC 15909-2. This way, we hope to unify the different lines of PNML and advertise the use of ISO/IEC 15909-2. Note that this paper is not a copy or exact reproduction of ISO/IEC 15909-2 (which, including all Annexes, has more than 100 pages). Rather it is a restructured excerpt that focuses on the most important issues and abstracts from some technical details, which can be found in ISO/IEC 15909-2. Most of the technical details can be derived from the RELAX NG grammars provided at the PNML web pages [17]. Together, this should provide a fair account of the standard, its ideas and concepts, and its practical use. For a in-depth discussion of the rationales and design decisions behind PNML, we refer to the bunch of earlier publications [2, 15, 4, 18, 19] Though not an exact copy of ISO/IEC 15909-2, this paper reuses material of ISO/IEC 15909-2 with some modifications and simplifications with the kind permission of ISO/IEC, Geneva. Originally, PNML was introduced as an interchange format for all kinds of Petri nets [2, 3, 4]. Some major concepts of PNML were driven by this objective. Technically, ISO/IEC 15909-2 defines a transfer syntax for High-level Petri Net Graphs and those subclasses of Petri nets only that have been conceptually and mathematically defined in the International Standard ISO/IEC 15909-1 [5], for capturing the essence of all kinds of coloured and high-level Petri nets [6, 7, 8, 9, 10, 11, 12, 13]. In this paper, the focus is on PNML for high-level nets in order not to mix up concepts that are part of ISO/IEC 15909-2 and some extensions, which are currently under consideration for ISO/IEC 15909-3. In the conclusion (Sect. 5), we will briefly discuss some of these perspectives, which make PNML applicable for all kinds of Petri nets.