Re: A few things I noticed about w3c's xml-schema

[Rick Jelliffe <ricko@allette.com.au>]

From: "Murali Mani" <mani@CS.UCLA.EDU>

> I also *fully* agree that RELAX NG is the most important thing that is
> happening at present.

But the point is that it is _still_ happening: the different flavours of
RELAX were not good enough for James' criteria so he made TREX; TREX is not
good enough for Murata-san so they are co-operating on developing it
further, over at OASIS.

If James, one of the keenest technocrats around, is still working on a
language after more than a decade experience with DTDs, with reviewing the
efforts of the XML Schemas WG, and after consideration of the seminal DSD
and RELAX, what does that suggest?

It suggests to me that _any_ standard for schemas must be considered either
premature or interim, at the current time.  And this is exactly the approach
that the XML Schema WG has taken: XML Schemas 1.0 is provisional both in
small matters  (because of the work of XML Schemas 1.1) and in larger
matters (the mooted XML Schemas 2.0).

Murali carpets W3C XML Schemas as bad, but he is in fact only interested in
one area of them.  The areas of datatyping, schema construction, keyrefs,
name handling have all been pretty well received: even though they are all
amenable improvement (respectively localizable datatypes, modules, better
keyrefs, status of schemaLocation).   (These are things I hope XML Schemas
1.1 will improve.)

The areas that have not been well received are
  -- perceived complexity of the spec (though complexity of the spec and
complexity of the technology are not at all the same thing: looking at the
two diagrams in the specs shows there is not spaghetti at the top-levels)
  -- type derivation (is it very useful for non-databases?)
  -- the details of the grammar    (is it overly
restictive/under-powered/unreasonable)

I don't see RELAX NG as a competitor to XML Schemas; to the contrary, I
think we can only ascend to XML Schemas 2.0 when there are credible
alternative languages developed and deployed, by which we can judge XML
Schemas 1.n.    (It is dialectic development.)

So RELAX NG is the best friend of the XML Schema WG, in the long run: it is
their unofficial research lab.  I don't know if Murata-san works on company
time on RELAX-NG, but I were his manager at IBM I would allot him spend as
much time as possible on it, because of IBM's commitment to XML Schema.  If
he is working on company time, then IBM should be congratulated.

RELAX NG may be just as important for XML Schemas 2.0 as the XML Schemas 1.1
standards work.  But I hope deployment experience from XML Schemas 1.n will
be much more influential than any speculative analysis: I think speculative
analysis is the methodology used both in XML Schemas and RELAX NG and
ultimately it provides no guarantee of producing a productive result.   When
a spec is made by committees sitting around the globe making up user
requirements on the spot as needed to justify their technological and
aesthetic predelictions, with no regard for how humans think and act, the
emperor has no clothes, no matter how relaxing he may find it.

An alternative take on all this would be that, if grammars (one of the most
exhaustively studied abstractions) introduce problems (such as the problem
with
adding or substracting schemas from each other) that are still (after 16+
years of schema language development) then perhaps they are dense and
compelling distractions which are actively preventing us from adopting more
straightforward
schema paradigms.

Cheers
Rick Jelliffe