The keys for normative references [XML], [XSD1], and [XSD2], appear once and only once in the draft.

If the normative references are not used, why list them as normative references?

BTW, under 4 XML Schemas, saying:

"The structural document constraints of the envelope are expressed normatively as a set of W3C XSD XML Schemas."

Is NOT an invocation of a normative reference by key.

Using this case as an example, invocation of the XML schema normative references could read:

The structural document constraints of the envelope are expressed normatively as a set of W3C XSD XML Schemas. [XSD1], [XSD2]