The PNK, the PNML and the ePNK: What became of our dreams?

In Wolfgang Reisig’s group at the Technische Universität München and later at Humboldt Universität zu Berlin, we were strictly forbidden “to waste our time on developing tools for Petri nets” for a long time. Then, in 1997, Wolfgang Reisig was on a sabbatical at the International Computer Science Institute (ICSI), Berkeley, California, where he, after his presentations and talks, was repeatedly asked a simple question: “do you have a tool for this?” After he returned from this sabbatical, Wolfgang changed his tune and requested: “Ekkart! We need a tool!” Luckily, some of his group had been disobedient before and had started thinking of and developing a tool for Petri nets already. In particular, Jörg Desel and I had started dreaming of a universal tool for Petri nets already and had come up with a name for it: the Petri Net Kernel1 (PNK) [1]. Based on this dream, different versions and extensions of the PNK have been implemented over the years [2–5]. And, as a sideline, the concepts of the PNK strongly influenced the Petri Net Markup Language (PNML) [6] – even though one of the main motivations behind our original dream was to get away from the never ending discussions on file formats for exchanging Petri nets. Now, many years have gone by and several recent anniversaries and retrospectives concerning people and events within the Petri net community inspired me to have a look back at the original dream of a universal Petri net tool [1] and to see to which extend today’s ePNK [5] actually fulfills the original dream. This paper and the related talk are a first attempt of discussing and structuring some of these insights, and of relating our original motivations and expectations to the actual result in a very loose and informal way – starting with only a few of the original ideas [1].