效绵鼎 marking u assignment of tokens to the places of Petri net u=μ1，u2,u3,…ln p2 t2 pl tl p4 3 13 p3◼ marking µ : assignment of tokens to the places of Petri net µ = µ1 , µ2 , µ3 , … µn 13 p2 t1 p1 t2 p4 t3 p3