Precisely. I'd like to be able to tell that application to create a single
instance from the trees (in whatever shape they arrive) under certain
circumstances. Having to guess whether an application will do so makes the
tools far less useful.
The use by reference/use by value distinction is important, but made painful
in practice by the fact that XML has an infinitely richer vocabulary for use
by reference than it does for use by value. Entities are extraordinarily
limited when compared to the rich possibilities XPointers open up, and I hope
that for many, though of course not all, uses entities (and notations as well)
will be effectively obsoleted.
Maybe Ted Nelson's right, and all this markup stuff gets in the way of proper
transclusion.
Simon St.Laurent
Dynamic HTML: A Primer / XML: A Primer (January) / Cookies (February)