It is certainly worth remarking on half a century of a work defining a landmark in Discrete Event Dynamic Systems (DEDS) theory. This invited contribution aims to combine some historical facts with elements of a conceptual view on concurrent DEDS, giving pointers about the development of the field. Simplifying the historical trajectory, it can be said that the seed sown by Carl Adam Petri in 1962 first grew in America (essentially until the mid 1970s), where an appropriate intellectual ambiance existed in computer science, business process management and switching systems design. Later, many other new lines of activity, including logic control and performance evaluation, flourished in Europe. Today Petri nets are widespread all over the world. The conceptual paradigm of Petri nets deals inter alia with modeling, logical analysis, performance evaluation, parametric optimization, dynamic control, diagnosis and implementation issues. In summary, multidisciplinary in themselves, formalisms belonging to the Petri nets paradigm may cover several phases of the life-cycle of complex DEDS. Given the hundreds of research and text monographs on Petri nets, together with the many thousands of theoretical and applied contributions on the subject, not to mention the ISO (International Organization for Standardization) or IEC (International Electrotechnical Commission) standards for the use of Petri nets in engineering, this work cannot hope to be a complete survey or a tutorial in the more classical sense. It is more of an impressionistic overview of the field. (C) 2013 Elsevier Ltd. All rights reserved.
