🚀 go-pugleaf

Surely the answer is not "a ubiquitous SGML entity manager" (Eliot 
Kimber) since that would be proprietary to SGML. I would rather see
a _general_ entity manager, and have PUBLIC references map on to
that in some standardized way.  I'm not suggesting that the scope of
SGML PUBLIC entities be made more general, just that that set should
be a subset of a much larger set of entities.  To me, the obvious
candidates for this would be X.500 or ISO 10031 (DOA).  (I haven't
gotten round to reading about DFR yet.)  Note that this would _not_
involve changing SGML; it would be saying that a PUBLIC reference is
a human-readable shorthand that expands into a reference to somewhere
in the SGML-entity subset of all referable objects.