XMI24 — what, if anything, is normative in XMI 2.1

In the conformance section of 05-09-01, all mandatory conformance points are given in terms of the rules (for schema and document production) defined in the specification. Are these rules the extent of the normative part of the specification?

In particular, there is a reference in 05-09-01 (section 2.3.3) to "Use of the normative XML Schema model by instantiation,…" It is unclear what "XML Schema model" refers to. Should there not be a reference to (what I presume to be) the XML Schema standard(s), thush leaving the sum total of the normative nature of the spec the rule sets mentioned above? Or, if the intent is to name the XMI Schema Infoset model in Chapter 8 as normative, why isn't the proper name used, along with a section reference?

Finally, there are fragments of an XSD file for XMI in section 4. Why is there no XMI.XSD file disseminated by the OMG? I suppose one could put together such a file by copying the text from the spec, but why bother?

XMI Schemas must be equivalent to those generated by the XMI Schema production rules specified in this document.
Equivalence means that XMI documents that are valid under a schema produced by the XMI Schema production rules
would be valid in a conforming XMI Schema and that those XMI documents that are not valid under a schema produced
by the XMI Schema production rules are not valid in a conforming XMI Schema.