XMI12 — DTD rules unclear for attributes of subclasses.

This issue relates to the description of production 4c of the simple
DTD ruleset on page 7-88. The text says

"If the Class has subclasses, the element name of each of its
subclasses
is included in the declaration".

This is ambiguous.

Suppose that we are generating a DTD for a Package P1 that contains C1,
and there is also Package P2 that imports clusters or inherits from P1
and defines C2 as a subclass of C1. In each case, should the DTD
generated for C1 in P1 include declarations for C2 attributes, or not?

If yes, how does the generator find out what packages import / cluster
/ subtype P1? Also, how does XMI deal with addition of (say) a new
importer of P1 after the DTD for P1 has been generated? (Does it
break?)

If no, how do I represent in XMI a link in an Association in P1 that
has a C2 instance at one end?

[I can guess some answers to these questions, but that isn't good
enough.
The spec should cover this Package composition issue here, or there
should
be a reference to some other part of the spec that deals with it.]