XMI12 — DTD element content and multiplicities versus compliance.

In XMI 1.0, the DTD generation rules give a DTD that "tightly" specify
the element content and multiplicities for Attributes according to the
meta-model types and multiplicities. In XMI 1.1, the generation rules
(at least the EBNF version) "loosen" the element content and
multiplicity.

The current XMI conformance rules have the effect that an XMI 1.0 DTD is
not conformant to XMI 1.1. Is this intentional? Should 11.2.1 bullet
point 4 be amended to account for different degrees of looseness?

I argue that:

1) Tighter DTDs should in general be compliant. A "tight" DTD that
constrains element content to meta-data that matches a meta-model
shouldn't be deemed non-compliant. The real point of XMI DTDs is
to ensure supposed XMI documents contain meaningful metadata, as
far as possible. It is counter-productive to make it "incorrect"
for an XMI DTD generator to do a better job than the templates.

2) A specific statement on backwards (in-)compatibility should be
added to deal with the sub-cases where XMI 1.0 DTDs are over-
constrained according to XMI 1.1; e.g. where the XMI 1.0 DTDs
constrain the order of elements representing Attributes.