type Weight = Multiplicity;
Multiplicity of a harc (a monomial when attached to a node).
Weight of a monomial occurring in effects of a node indicates the number of tokens to take out of that node if a corresponding transaction fires. Weight of a monomial occurring in causes of a node indicates the number of tokens to put into that node if a corresponding transaction fires. Accordingly, the weights imply constraints a state must satisfy for a transaction to fire: a minimal number of tokens to be supplied by pre-set nodes, so that token transfer may happen, and a maximal number of tokens in post-set nodes, so that node capacities aren't exceeded. The ω weight attached to effects of a node indicates that the presence of any token in that node inhibits firing.