Annotation issue: what should a:attributeType be attached to?

Should the a:attributeType be attached to the <attribute> element or to the 
element specifying the pattern for the value of the attribute?

In trying to update XHTML to use the annotations instead of key/keyRef I 
encountered a problem.  There was a definition:

<define name="IDREF.datatype">
  <keyRef name="id">
    <data type="NCName"/>
  </keyRef>
</define>

This IDREF.datatype definition is referenced in the patterns for several 
different attributes.  There's no way to translate this definition given 
that a:attributeType is attached to <attribute> elements; instead the 
a:attributeType annotation has to be repeated for each <attribute> element.

On the other hand if we put the annotation just on <data>, then we will run 
into the same problem that we did when we had key/keyRef attributes on 
<data> rather than as separate elements.

How about saying that a:attributeType goes on any element that, in the 
simplified schema, occurs as the child of <attribute>?  Should we allow it 
on <attribute> as well?

James