XMI12 — XML attribute encoding of values underspecified

Assuming that XMI 1.2 retains XMI 1.1's optional encoding of DataType
values as XML attributes, the specification needs to be fixed as follows:

• It should list that DataTypes that can be encoded in two ways,
  how they are encoded, and the meta-model and runtime contexts under
  which this is legal.

• The spec should say how a decoder should deal with anomalies like
  the following:

<some.attr xmi.value="1">1</some.attr>

<someother.attr xmi.value="1">2</someother.attr>

<multi.attr xmi.value="1" />
<multi.attr>2</multi.attr>

<string.attr xmi.value="hi">
</string.attr>

Which (if any) of the above is legal?

• The spec should state explicitly that a decoder that does not
  look in both the xmi.value attribute and the content is not
  XMI 1.2 conformant. [Not that this helps much in practice :-(]