XInclude also limited

Declare on every reference Unlike entities, which can be declared once and used repeatedly, XInclude references are declared in full every time they are used
External only XInclude (reasonably, given its verbose mechanisms) is only designed to point to external resources.
Ambiguous model XInclude elements are just plain XML elements. This is fine, unless you expect them to get processed in environments you don't control. They'll just kind of turn up in the document if someone goes to look at it.
Another layer on top of XML parsing The Infoset-based approach puts all of this on top of the parsing layer in XML. Where does it go? Could I create schemas which include definitions of where XInclude elements should go? Should I create schemas which describe the structures of documents after the XInclude is done? How do I indicate which to use when? This wasn't a problem before.