Jeff: I agree but the only reason I used sub site is because the parameter page offered to set parameters of package instances is defined in acs-subsite as well as the parameter::set_value proc. So this is a acs-subsite problem, right?
Roc: Changing parameters is not a daily thing. What happens when a parameter changes application specific. No developer will every need to do extra coding. You only offer a callback implementation if you package depends on values of parameters set in other packages. This is actually very convenient.
