XMI12 — DTD production clarifications for nested Packages

When a Package contains another Package:

a) If the containing Package contains an Association which is only
referenced in the contained Package, should the containing Package treat
it as an unreferenced or referenced Association?

b) If the contained Package contains a child Class which inherits
from a
parent Class in the containing Package, should the DTD for the
containing
Package allow instances of the child Class?