[tei-council] Conformance draft: namespace purity

[Conal Tuohy]

On Mon, 2007-04-02 at 23:30 +0100, Sebastian Rahtz wrote:
> I would strongly suggest that people use something
> based on their project URL if they have one.

I agree.

The W3's architecture document "Architecture of the World Wide Web"
includes some relevant guidelines, including this one about "namespace
documents":

http://www.w3.org/TR/webarch/#namespace-document
> Good practice: Namespace documents
> 
>  The owner of an XML namespace name SHOULD make available material
> intended for people to read and material optimized for software agents
> in order to meet the needs of those who will use the namespace
> vocabulary.

Here "an XML namespace name" means the namespace URI itself, and
"namespace document" means a document you can retrieve from that URI.
The TEI namespace URI, for instance, identifies a document on the TEI
website which says that it's the TEI namespace, published by the
Council, that there's no plans for it to change, etc, and links to the
TEI guidelines themselves.

So I think if people are using ODD to make a custom schema in which they
add new elements, it is good practice for them to publish information
about those changes in a "namespace document". A good way is for their
namespace URI to be an http URL pointing to a location where they will
publish that information. e.g. If a project were to publish their ODD
file on their website, that ODD file could itself be a good namespace
document.

But I think this W3 guideline implies we should not suggest an http URI
which starts with "http://www.tei-c.org/ns/user-defined/" (or similar)
because that might imply that we would be maintaining a register of
customisations. The namespace URI should clearly belong to the person
making the customisation, not to the TEI Consortium.

However, if the project doesn't have a website, then it might prove a
barrier to provide a "namespace document". During the development phase
of a project, it might not be clear what namespace URI would be best, so
a temporary URI might be needed. In such cases, rather than use an HTTP
URI, they could use some other kind of URI, such as a "tag" URI, e.g.

"tag:conal.tuohy at gmail.com,2007:xmlns/my-customisation"

The syntax of a tag URI allows for people to mint one based on their own
email address, so the barrier to use is low. 

Tag URI syntax:
http://www.taguri.org/07/draft-kindberg-tag-uri-07.html#SYNTAX

Cheers

Con