XMI12 — The "complete" approach to XMI data types must be optional

The XMI 1.1 RTF added material to section 6.5.18 to allow XMI DTDs
to be defined (by the metamodeller) that use custom XML elements to
represent data values. This is the so called "complete" approach,
and is new in XMI 1.1.

The description of the "complete" approach in section 6.5.18 and
elsewhere seems to allow XMI DTDs to be created by hand that cannot
be automatically generated from a meta-model. This means that the
"complete" approach cannot be implemented by a MOF / XMI vendor
without relying on proprietary extensions; e.g. a proprietary way
of telling XMI generators for import and export tools how to
encode / decode custom data strings.

At a minimum the "complete" approach should be downgraded to an
optional
XMI compliance point in XMI 1.2 It could be argued that the material
should not have added in the first place, since:

1) adding significant new functionality is beyond the scope of
an RTF, and

2) incomplete specifications that rely on "magic" or on proprietary
extensions are forbidden.