In: Journal of Information Processing and Cybernetics, Vol. 24, No. 1-2, pages 3-18. 1988.
Abstract: A semantics describing the concurrent behaviour of Petri nets either implicitly assumes a global clock pulsation synchronizing the net or it does not regard any outer time dependencies. It is shown that both approaches are equally powerful. In particular, this means that the introduction of a global clock does not coincide with a loss of information on causal dependencies.