I've seen the XML Schema Type Library's "text" type,
supporting arbitrary mixed content. I have been unable to figure out how
to define a complex type whose contents are any simple type value or any single
element, but not a mixture, where an element of this special type has a certain
set of attributes That is, I'm trying to define
??? some kind of restriction of anyType with
either simple or complex content
so I can say in instance docs
<foo a="x" b="y"
<foo a="xx" b="yy"
I think I need a disjunction of simpleContent and
complexContent but am uncertain how to produce this.