No species charge
charge on the SBML Species component has been deprecated for some time. It was an ill-conceived attribute that had little utility. First, the value of
charge has never been accessible to the mathematics of the model, therefore it cannot actually be used in any operational way. Second, if a species exists in a model in two different charged states, those different versions of the species constitute two different pools, which means that in Level 2, they should be represented as two separate species (perhaps having the same species type).
For Level 3, this deprecated attribute will be removed entirely.