> On Wed, 2002-06-19 at 23:35, Michael Fitzgerald wrote:
>> Future plans for Trang [http://www.thaiopensource.com/relaxng/trang.html]
>> include an output module for XML Schema.
I am implementing this at the moment.
> The problem with this approach is that Relax NG is more "free style"
> than W3C XML Schema and that many Relax NG schemas cannot be easily
> translated into WXS.
If it was easy, it wouldn't be any fun.
> In other words, if you want to be compatible with both technologies, WXS
> will be the limiting factor and you need to take it into account first.
I don't agree. It's the job of the user to express their intent as simply
and clearly as possible; RELAX NG is ideal for this. It's the job of the
machine to go through all the bizarre contortions that are required to turn
this into a W3C XML Schema. If the user writes something that cannot be
expressed in W3C XML Schema, then the machine should do what a human would
do: find the constructs that permits everything that they want to permit
and permits as few things as possible that they don't want to permit. For
example, if a user wants a choice of attribute A or attribute B, then they
should express that intent in RELAX NG. The machine can tell that this
cannot be expressed in W3C XML Schema, can inform the user of this and turn
it into optionally attribute A and optionally attribute B. One could even
imagine it automatically generating an annotation containing a Schematron
rule that checked that exactly one of A and B was present. When W3C XML
Schema 1.1 or 2.0 adds support for this, they will be able to take
advantage of this without changing their schemas.
Completely realizing the above vision is no trivial task and the first
version of XSD support in Trang will fall short in many ways. However, I
think it's important not to get too hung up on technical details that to
most users are obscure and unimportant. Many users make relatively simple
use of schemas.
James
