Suppose I have the following Petri net:
I wonder whether it is possible to model an inverse relationship between $p2$ and $p3$. Basically what I want to achieve is to make either $t1$ or $t2$ fireable but never both. Currently, I just set a token in $p2$ and leave $p3$ empty if I want to make $t1$ fireable (or vice versa for $t2$). I believe there must be a way to omit one place and achieve the same result, i.e., putting one token in $p2$ activates $t1$ but not $t2$ and zero tokens in $p2$ achieves the reverse.