XMI21 — Schema production rule 4d clarification request

Document refs are against formal/03-05-02.

Maybe it's because I'm still struggling with the details
of XML Schemas and MOF, but I'm confused with rule 4d of
the XML Schema Production rules (EBNF on page 2-4, expla-
nation on page 2-5).

• According to the EBNF, a type='xmi:Any' is an output
  option, but according to the explanation, this option
  is never used.

• The explanation goes, "The type is 'xsd:string' for simple
  attributes ..." It is not clear to me what constitutes a
  "simple" vs. "non-simple" attributes. I assume this refers
  to MOFs PrimitiveTypes, but in any case a clarification
  would be useful.

• The explanation goes on, "The type is [...] part of the
  of the value of the org.omg.xmi.schemaType tag". Why does
  it say "part of"? What should be removed from the value?

• There is also a question of precedence. I guess the
  intention is that the schemaType tag should take
  precedence over the "simple attribute" decision?

• There is no "else:" What if the attribute is not simple,
  not an enumeration, and the schemaType tag is not set?
  (Or maybe that is not possible in MOF?)