Annotation issue: other attribute types

Should we allow a:attributeType to take values other than ID/IDREF/IDREFS?

For example, one could allow it to take the value of NOTATION or ENTITY, 
which would imply the same checking that XML 1.0 does (ie that it would 
refer to an ENTITY or NOTATION declared in the DTD of the document not in 
the schema).

Even NMTOKEN and NMTOKENS could be useful for infoset modification 
(attribute value normalization) that they imply.

James