Closing Remarks

In the 1960s, Carl Adam Petri’s proposals for the modeling of discrete, asynchronous systems were too advanced for practical application and the “wrong” topic for the theory at that time. Accordingly, the responses were limited at first, but at least the MAC project at MIT picked up Petri nets in the late 1960s. In the 1970s, Petri nets were often used (inappropriately) to characterize formal languages. The reachability problem was long regarded as the central challenge in this area. In the early 1980s, “colored” tokens significantly increased the expressive power of Petri nets, and modeling tools enhanced their applicability in larger projects. At the same time, Petri nets entered into a fierce competition with other modeling techniques. The general interest in modeling techniques, especially graphical ones, which had been growing since the 1990s, eventually established Petri nets as an important contribution to computer science. Since 1979, an annual conference, summer schools, workshops and anthologies on specific topics have come on the scene. The number of publications on Petri nets is in the five-digit range.