Re: [xml-dev] The purpose of a namespace URI is ...

[Dan Vint <dvint@dvint.com>]

This is an ok alternate way of getting the same effect, but it is not 
supported universally. For instance XML catalogs I don't believe will 
work with this. Just like PIs they give a method for mapping URIs to 
a file location. I work with the S1000D standards and each major 
release of those schemas provides a unique URI for reference.

The Public Identifier provided a good mechanism for identifying the 
vocabulary of a document, why was this not carried forward with Schemas?

..dan

At 03:59 PM 12/1/2012, Liam R E Quin wrote:
>On Sat, 2012-12-01 at 12:44 -0800, Dan Vint wrote:
> > Coming from the SGML world, I prefer to think of them as a Public
> > Identifier in a different format.
>
>This is not a good way to think of a namespace URI.
>
>There are some things in common - a namespace URI is a name - but some
>important differences:
>. Public identifiers in SGML are dereferenced indirectly (officially by
>sending a fax to ISO last time I checked but that was a long time ago);
>there's no expectation that anyone will ever try to dereference a
>namespace URI (people do, because it looks like you ought to be able to,
>and some people like to put human-readable explanations of the namespace
>at the namespace URI, but there's no guarantee and software should not
>do this automatically)
>. Public identifiers explicitly contain versioning in their syntax. Two
>public identifiers differing only in version or in language are known by
>SGML software to be related. Two namespace URIs differing by even as
>little as a single bit are considered 100% unrelated by namespace
>processing software, and are not expected to refer to similar things at
>all.
>
> >  I process documents and I don't
> > typically use JAVA or other programming language to deal with them.
> > As such, I prefer to have a unique identifier for versions changes.
> > If not for minor changes, anything that introduces a change that
> > would break backward compatibility should be identified.
>
>It's usually better to do this with a version attribute rather than to
>use a new namespace URI and thereby claim you're making a new and
>entirely unrelated language.
>
>Liam
>
>--
>Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
>Pictures from old books: http://fromoldbooks.org/
>Ankh: irc.sorcery.net irc.gnome.org freenode/#xml

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