Sophie wrote:

> It uses two arrows to indicate that you need 2 Hydrogens for the reaction. How would you represent this in a wiring diagram? Two wires labeled with the same resource?

Yes, exactly. It would be nice for someone to draw an example or two where this kind of thing happens.

Note that a Petri net specifies a way of making a commutative monoid \\(\mathbb{N}[S]\\) into a commutative monoidal preorder, while a wiring diagram specifies a proof of a given inequality in that commutative monoidal preorder.