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RE: Namespaces, schemas, Simon's filters.


> -----Original Message-----
> From: Tim Bray [mailto:tbray@textuality.com]
> Sent: Friday, August 24, 2001 6:05 PM
> To: xml-dev@lists.xml.org
> Subject: RE: Namespaces, schemas, Simon's filters.
> At 05:19 PM 24/08/01 -0700, Evan Lenz wrote:
> >if what you mean by
> >"element types are global" is that there is always a one-to-one
> >correspondence between an element name and a content model.
> Ron, is this what you mean?  Has anyone ever argued that there
> should be a 1-to-1 linkage between name and content model (or
> any other set of semantics)?

A DTD establishes a 1-to-1 linkage between an element name and a content
model, as well you know.  A schema (without local elements) establishes a
1-to-1 linkage between an element name and a complexType.  You can munge
this in a out-of-band way by playing with the DTD or Schema, but certainly
in the context of a single validation, there is such a linkage.  If you are
validating Ron is right, or right with the slight suggestions I've made.

If, on the other hand, you are in the well-formed world the, yes, namespaces
only help create vocabularies, but you're free to assemble documents from
those vocabularies any way you want - there's no content model.  But don't
dis the validators.

> >#2 was never true for me in the first place. In fact, I 
> would consider the
> >use of namespaces to be orthogonal to the use of local element types.
> Yes!  Anyone disagree?

I'm not Evan means what you think he means, as he later agrees that local
names should not be in a namespace, which you seem to vehemently disagree
with.  In any case, namespaces are just a mechanism which can be used in a
variety of ways.  I believe the use of namespaces is related to what you're
using them for.  In particular, I believe they were intended to help
disambiguate things, to uniquely identify things.  If you are working with
Schemas, rather than in the well-formed world, then namespaces should be
used to disambiguate the kinds of things you can define with a Schema.

> >Yes, and so it should, and so they should. In my world, 
> types and names are
> >not necessarily the same thing.
> I agree.  Unfortunately, XML 1.0 uses "type" to mean "name",
> essentially.  I think Evan has hit the bull's-eye here. 
> Are we making progress? -Tim

However, Schemas and DTDs link names and types.  If you're also using
namespaces with a Schema, shouldn't the namespacing help elucidate those