XMI21 — Are xlinks legal?

maybe this is just because of my ignorance, but I'm running into
a problem trying to validate documents against an XMI based schema
here, and it looks like the validator has a point.

As usual, my base document is XMI 2.0, formal/03-05-02.

Section 1.10.2 "Linking" describes the usage of XLink simple links
and XPointers to link across documents.

However, looking at the schema production rules (page 2-2 to 2-5,
rules 4g:ClassAttListItems and 1g:XMIFixedAttribs, as well as the
LinkAttribs attributeGroup in the Fixed Schema Declarations on
page 2-10, the xlink:href is never declared as a legal attribute
for complexTypes.

Hence I see why the parser (Xerces-C, when requested to validate)
complains about attempts to use XLinks in a document.

I think it is paramount that documents validate against the schema.
(Am I the first to attempt validation? Can't be.)

I realize that there doesn't seem to be a schema for XLinks yet,
so the short-term solution might be to allow the "normal" href
attribute to contain an XPointer.

As a minor nitpicking, page 1-23 gives the XLink namespace as
"http://www.w3.org/1999/XLink", whereas the W3C recommendation
for XLink uses "http://www.w3.org/1999/xlink" (note case).