Some Remarks on D-Continuity

One afternoon in 1978 (or was it in 1977 ?), C.A. Petri called one of the authors of this paper to his room. He wanted to talk about some “axioms of concurrency”. By that time, we knew already that a non-sequential process -viewed as a record of conditions-holdings and events-occurrences of a system- could be modelled using a special type of net called occurrence net, [7], [6]. Since at the behavior level, cycles are unrolled, one may associate to each occurrence net a partially ordered set, poset for short, which is an appropriate mathematical machinery to study non-sequential processes.