I would certainly like to be able to declare in a DTD that
certain elements are valid roots and others are not.
Assuming there is technology to validate a document against
an XSchema, it moves one more validity check out of my
application and into the schema.
In the DTDs I have written, very few of the element types
(often just one) are valid roots, so my own choice of
default would be INVALID.
MIke Kay