# Places, transitions, arcs (and only one kind of arc) PNConnectable:Class { abstract = True; } arc:Association (PNConnectable -> PNConnectable) PNPlace:Class PNTransition:Class # inhibitor arc inh_arc:Association (PNPlace -> PNTransition) :Inheritance (PNPlace -> PNConnectable) :Inheritance (PNTransition -> PNConnectable)