With the greatest respect, John, I see it quite differently.
I propose that our job as priests is not so much to do the singing, as
we generally do. Instead, it is to help *everyone* sing, thus to enter
into the joy of a more functional, integrated, interdependent and
prosperous community.
What you see as elegance, I see as beautifully-wrought art based on the
assumption that a priesthood of parserheads will be the primary users.
It's great for people like us, but it's less comprehensible and less
universally available to everyone else. Most of humanity, including the
people who are more qualified than we are to make domain-specific
decisions with economic, political and technical consequences, is better
equipped to learn the clunky old DTD syntax.
(I freely admit it's a bitch to parse. But natural language is much
harder. Another demonstration that human communication is quite
different from machine "communication".)
Everyone writes documents. Everyone knows what a telephone number is,
and the local rules for constructing one. But comparatively few people
know what a data type is, much less the traditional primitive datatypes,
or any but the vaguest notions about relational databases. If we bear
those facts foremost in our minds, while ignoring everything we know
about computing, we may begin to suspect that the whole endeavor of
bringing strong data typing into the world of document interchange was a
trip into the weeds, at least from the most general perspective of human
communication and the world economy.