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Re: CSS Namespaces: Need multiple namespaces!

From: Ian Hickson <py8ieh@bath.ac.uk>
Date: Thu, 30 Sep 1999 23:26:48 +0100 (BST)
To: Chris Lilley <chris@w3.org>
cc: www-style <www-style@w3.org>, "L. David Baron" <dbaron@fas.harvard.edu>, peterl@netscape.com
Message-ID: <Pine.GSO.4.04.9909302317560.16589-100000@ss1.bath.ac.uk>
On Thu, 30 Sep 1999, Chris Lilley wrote:

>> When|If Schemas are pointed to by namespace URIs (as suggested in
>> various packaging ideas recently), then namespaces will fill
>> basically the same role as PUBLIC/SYSTEM FPIs/DTDs, and so n (where
>> here n=3) namespaces will become a necessity.
> So in each DTD/XSchema that uses a given vocabulary set, it has a
> different namespace identifier, then there is no ability to
> recognise different namespaces.

Sorry, I don't follow that.

> So you have made namespace declarations be an exact analogue of
> doctype declarations, which already exist, and removed the ability
> to identify which vocabularies are being combined in a given
> document.


The problem with DOCTYPEs is that they can only appear once in a
document. The ability of identifying which vocabularies are used in a
document is done by the xmlns attribute(s), which can appear as often
as required. The content of these attributes is an arbitrary unique
string. This string uniquely identifies a namespace. Each namespace
can have a Schema (just like each FPI has a DTD).

So just like the <!DOCTYPE> points to the DTD, it makes sense for the
xmlns= to point to the Schema.


If this is not the case, then what _is_ the difference between
namespace declarations and doctypes?

(Note -- I make two assumptions which may be flawed: 1. Schemas are
basically souped up DTDs, and 2. each namespace will only have one
Schema. Are these assumptions correct?)

Ian Hickson
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Received on Thursday, 30 September 1999 18:26:51 UTC

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