Re: using namespaces to version

[Warren Hedley <w.hedley@auckland.ac.nz>]

Hi David,

David Carlisle wrote:
> 
> It seems to me that two languages with no names in  common are not
> versions of each other but rather two different languages.

That's a good point. I'm not convinced that this isn't really the
case though, as far as processing software is concerned, for instance.

One of the tools that I want to provide is a validator for my language.
If the content model of an element changes between versions, then it
seems to me that I have no way of telling if the document is invalid
or not.

Take the replacement of <reln> with <apply> in MathML 2.0. My imaginary
MathML validator (that can validate against 1.0 and 2.0) is unable to
detect if a document is 1.0 or 2.0 unless it includes elements that are
new to 2.0. For instance, it doesn't know if it should reject
<apply><eq /> and suggest using <reln><eq /> (<eq> was not listed as an
operator in MathML 1.0 I believe), or not.

Wouldn't it be useful to have the namespace on the <apply> element define
what the correct content model is? I don't really see the problem in
having:

<http://www.w3.org/MathML/1.0#apply> and
<http://www.w3.org/MathML/2.0#apply>

Whether a specification allows the combination of elements from different
version is up to that spec.

> ... all existing XPath queries into MathML structure (for
> example) will not apply to this namespace.

This is a really compelling point, as my validation is currently based on
XSLT. Certainly a template-based stylesheet that does formatting won't be
too concerned about the version of the document it is applied to. To a
computationally oriented stylesheet this will be important however.

I'm going to have to think about this a bit more, obviously.

Thanks,
Warren

-- 
Warren Hedley
The Bioengineering Research Group
The University of Auckland
New Zealand
-- 
Warren Hedley
The Bioengineering Research Group
The University of Auckland
New Zealand