The XML-dev
mailing list has recently seen a lively and
informed debate as to the value of a single schema
language and centralized schema repositories.
The debate was initiated
by Matthew Gertner, who announced that he had
posted a short
"XML Rant" arguing for a standard schema
language and schema repository.
Rick
Jelliffe responded that while he agreed there
ought to be a standard schema discovery mechanism,
there should not be a standard schema language:
"Every schema language is built on a zillion
trade-offs. The best we can
hope for is that a schema language will be
wonderful on some major
application domain and not entirely useless
generally."
In other parts of the debate, attention focused
on schema repositories, and whether the goal of a
unified repository was possible.
Tim Bray commented:
"I share the doubt that a grand unified schema
repository will be tractable
to build & maintain. I also am
enthusiasm-challenged because in my (lengthy)
experience with XML and its ancestors, I have only
ever seen machine-readable
schemas put to use in one application: namely the
use of DTDs in
hand-authoring XML documents. "
Don Park shared
the scepticism, saying "My opinion on unified
schema repository is that it won't happen while
everyone is interested in it because expectation
leads to escalating hype
and politics." He went on to share a vision of a
schema bridge service which would convert between
schema languages, and an ultimate "Unified Schema
Bridge Registry".
The whole thread, spanning several days in the
archives, is worth reading for an excellent tour
of the issues involved in schemas, and their
description and discovery.