Analysis of the Example
As previously commented, a PN-state can be represented in matricial form as:
Mi = [q1 q2 q3 q4]T, where qi indicates the quantity of tokens in place Pi.
The next state after firing transition tj is given by Mi+1 = Mi + C · ej, where ej is the characteristic vector for transition tj, a column vector with 1 in position j and 0 in the remaining positions.