Why would you want to do that? Entities explicitly live in the user's
namespace and I think that it is good that they should have complete
control over their names. I can't imagine why a schema designer would
complain that they were using the "wrong" definition. It seems to me that
that would be like complaining that they used the "wrong" namespace prefix.
SAX is relevant because it represents the communities combined idea of
what a typical application should expect from a typical parser. I can see
why an editor or database system might want more, but I don't think that
a schema language should. It isn't "in the XML spirit" to require
calisthetics from implementors for minor gains (verifying entity
replacement strikes me as a very minor gain).
Paul Prescod