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- From: <david@megginson.com>
- To: "XML Developers' List" <xml-dev@ic.ac.uk>
- Date: Fri, 15 Jan 1999 10:09:22 -0500 (EST)
Borden, Jonathan writes:
> This is the *current* state of affairs. There are people who also
> believe that in the future the namespace concept is to be extended
> to incorporate Schema definition. That is, when a namespace URN
> points to a Schema definition, the Schema may, can or will be
> enforced in the same way that a DTD is enforced by a validating
> parser and a <!DOCTYPE definition.
Ack! No! Please don't hardcode a one-to-one relationship between
schemas and namespaces.
A single schema could define structures using elements and attributes
from more than one namespace, and elements and attributes from a
single namespace can be used and structured in many different ways.
SGML people handle this problem in a fairly clumsy way by using public
identifiers for indirection and then swapping entity catalogues at
different stages of production. We can do better if do what a
database designer does for many-to-many relationships: add separate
associations between the namespace and the schema.
The alternative would be to rely on HTTP content negotiation to get
the kind of schema you want, and that is a pretty grim prospect
(especially for people with web sites hosted by large ISPs who really
aren't going to let them fiddle with the web server).
All the best,
David
--
David Megginson david@megginson.com
http://www.megginson.com/
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