I don't believe that I have ever written a DTD that *did* use the &
occurrence indicator in a content model.
I also don't believe that I have ever written a DTD (to be used more than
once) that did NOT use parameter entities.
If you invent enough subclassing/inheritance/content model reuse features,
you may be able to get away without them. But you can't just take them out
if you expect people to do serious document modelling in XML.
Paul Prescod - http://itrc.uwaterloo.ca/~papresco
"A writer is also a citizen, a political animal, whether he likes it or
not. But I do not accept that a writer has a greater obligation
to society than a musician or a mason or a teacher. Everyone has
a citizen's commitment." - Wole Soyinka, Africa's first Nobel Laureate