Temporal extensions of Petri nets
Petri nets: Theory and implementation

To take into account the quantitative temporal constraints of real-time systems, Petri nets have been extended with temporal information associated with places, transitions or arcs (see for a comparative study).

In these temporal extensions of Petri nets, two types of semantics can be envisaged for the flow of time. In the strong semantics, time flow cannot desensitize transitions, whereas in the weak semantics, all delays are allowed. In the strong semantic, time allows the modeling of a two-counter machine