@embray I was suggesting renaming the current `Parameter` class to `ParameterDescriptor` (or something else) and having a regular `Parameter` class which stores the value and other information if needed. This new `parameter` class can subclass `Quantity`. Why is it a bad idea to store the value of a parameter in `Parameter` instances owned by the model? I see it as equivalent to storing quantities with the option of adding more attributes if needed.