[dsdl-discuss] Re: Overlaying schema expressions

On Mon, 31 May 2004 12:36:52 +1000
Rick Jelliffe <ricko@allette.com.au> wrote:

> G. Ken Holman wrote:
>
> > But, in my understanding, a lot of people think that this is insane.
> >
> > Then it is time for us to proselytize, and I have a real-world
> > situation where I will try to bring this up.
>
> OTOH, the idea that there may be more than one schema per underlies XML
> Schemas type derivation
> by restriction, wildcards and substitution groups.

Disagree. They are mechanisms for creating schema components by reusing
diffrent schema components. In particular, when derivation by extension
is used, an element valid against a derived type is not valid against
the original type.

>And I don't think
> it is really so contentious that it is necessary sometimes to have
> different orthogonal schemas, e.g.
> anything + Schematron, to make up for shortcomings.

I see nothing wrong in that scenario. But have people use W3C XML Schema
together with Schematron?
 
> Well, everything on a computer has to be expressed in syntax (or
> something expressible in syntax). If you have this
> absolute distinction between syntax and semantics, then "semantics"
> reduces to "everything that cannot be expressed
> on a computer" it seems to me. But things only have syntax because
> they have semantics. So I don't really
> understand the whole argument.

Eri has already provided a very good explanation. He wrote: "Schemas provide a new
indirect way to attach the applications that implement the semantics
(the XSLT transformation in my example) to the labeled branch of the
 hierarchical tree. " I think that this indirection should not be mandated
but rather left to additional layers such as data binding tools.

CHeers,

-- 
MURATA Makoto <murata@hokkaido.email.ne.jp>
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