Problem
Consider the portion of a PN given in Suppose you want to model a requirement of the type "Once a token is produced in place P3, it can be consumed, either through transition t1 or through transition t2, within a time t„,,„. If neither of these alternatives happens, the token cannot be consumed any more." Show that timed PNs, as defined in this chapter, cannot describe such a requirement. Outline an alternative way of defining timed PNs that could cope with the problem.