Hierarchical Namespaces (was Re: ATTN: Please comment on XHTML (before it's too late))

[James Tauber]

Paul wrote:
> > > Namespaces should be hierarchic. I think that now most of XML
developers  would agree.

I wrote:
> > Namespace URI's are hierarchical already, so all it would take is prefix
matching. I briefly suggested this when
> > namespaces first came out and again in more detail in a couple of posts
last week.
[...]
> > p[starts-with(namespace-uri(),"http://www.w3.org/xhtml1/")]

Paul wrote:
> Maybe we have a different understanding of what is
> hierachical  ?

Perhaps I just didn't make myself clear :-)

> http://www.w3.org/TR/xhtml1/strict
>
> Do I understand right that version 2 would cause
>
> http://www.w3.org/TR/xhtml2/strict

Well, I don't know what the XHTML folk are planning, but it doesn't really
matter. If you just what XHTML regardless of version or strictness, you
would just say

starts-with(namespace-uri(),"http://www.w3.org/xhtml")

In other words, with prefix matching, you don't need to match exactly at a
directory separator "/".

> By the way -  XT is now using
>
> xmlns:xsl=http://www.w3.org/XSL/Transform/1.0
>
> This is smart. ;-)

I liked it too, but this may change in light of the current XHTML namespace
debate.

> In opposite , the article
> ( http://www.jclark.com/xml/xmlns.htm )
> ( by the same author! ;-) shows us:
>
> xmlns:HTML="http://www.w3.org/TR/REC-html40
>
> Isn't it *not* that smart?

You can still do prefix matching if they consistently use
http://www.w3.org/TR/REC-htmlXX

> Would't it be better to have:
>
> xmlns:HTML="http://www.w3.org/HTML/4.0
>
> instead ?

Probably, in as much as it keeps them free from their TR URL scheme, but, as
I note above, if one is just doing prefix matching, the "/" separator isn't
necessary (although I agree with you that it is neater to have).

> PS. Actualy there are still some more problems, but thinking
> about more complex things would be easier after I'l understand
> some simple things.

As I noted in an earlier post, any (single) hierarchical representation of a
set of features forces you to prioritize axes (ie pick one permutation). If
XHTML used:

http://www.w3.org/TR/xhtml1/strict
http://www.w3.org/TR/xhtml1/transitional
http://www.w3.org/TR/xhtml2/strict
http://www.w3.org/TR/xhtml2/transitional

You could specify for version and underspecify for strictness, but *not* the
other way around.

James
--
James Tauber / jtauber at jtauber.com / www.jtauber.com
Maintainer of : www.xmlinfo.com,  www.xmlsoftware.com and www.schema.net
<pipe>Ceci n'est pas une pipe</pipe>



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