Justify why there is no inherent measure of time or the flow of time in a Petri net. How
this reflects a philosophy of time which states that the only important property of time, from a
logical point of view, is in defining a partial ordering of the occurrence of events. Clarify how
events take variable amounts of time in real life, and how variability is reflected in the Petri net
model by not depending on a notion of time to control the sequence of events.