A Graphical Petri Nets Simulator - Rochester Institute of Technology

the firing of a transition is possible only
if the input places of a
transition hold a set of tokens required by the labels on the arcs from
the input place to the transition.
1.3.6 Predicate-Transition Nets (PrT-nets)
A PrT-net specifies the relationship between tokens and transitions.
The net contains a set of predicates associated with each transition
(inscriptions in the transitions); they
give the relationships between the input
tokens that are necessary for the transition to fire. In a PrT-net, a transition
can only be fired when the names match and the predicate is true.
1.3.7 Predicate-Action Nets (PrA-nets)
In PrT-net, predicates apply to the input places of the transitions and
operations give new tokens in output places. In addition, each transition has
an expression ofthe form "Predicate Action"
attached to it.
A PrA-net must be a safe net( that implies the weights of all arcs in the
net is one). In order to enable a transition in a PrA-net, the predicate
associated with the transition must be true, when the enabled transition is
fired the action attached to it will also be taken.
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