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Sunday, February 24, 2008

HTTP-based IETF Namespace URIs at IANA

The draft I-D "HTTP-based IETF Namespace URIs at IANA" creates a registry
and defines a procedure to allow IETF specifications to register XML
Namespace Names with IANA which are HTTP URIs and thus potentially useful
for looking up information about the namespace. Many IETF specifications
use Extensible Markup Language (XML) 1.0 (Fourth Edition) with Namespaces
in XML 1.0 (Second Edition). XML Namespace Names are URIs, and there are
many options for constructing them. One of the options is the use of HTTP
URIs -- those whose scheme is 'http:'. IETF RFC 3688 (The IETF XML
Registry) created an IANA registry for XML namespaces based on URNs,
which take on the form 'urn:ietf:params:xml:ns:foo'. RFC 3470 observes
that in the case of namespaces in the IETF standards-track documents,
it would be useful if there were some permanent part of the IETF's own
web space that could be used to mint HTTP URIs. However, it seems to
be more appropriate and in line with IETF practice to delegate such a
registry function to IANA... IANA maintains a registry page listing the
registered XML namespaces which use HTTP URIs. For each registered
namespace, the registry page includes a human-readable name for the
namespace, a link to the namespace document, and the actual namespace
URI. Namespaces created by IANA upon registration have the following form.
There is a common prefix, "" [...] followed
by a unique identifier. The unique identifier should be a relatively
short string of US-ASCII letters, digits, and hyphens, where a digit
cannot appear in first position and a hyphen cannot appear in first or
last position or in successive positions. In addition, the unique
identifier can end in a single '/' or '#'. XML namespaces are
case-sensitive, but all registrations are required to mutually differ
even under case-insensitive comparison. For uniformity, only lower
letters should be used. A unique identifier is proposed by the requester,
but IANA may change it as they see fit, in consultation with the
responsible Expert Reviewer. For each namespace registered, there must
be a namespace document in either HTML or XHTML which may be retrieved
using the HTTP URI which is the registered namespace name. It contains
the template information with appropriate markup. The request for creation
and registration of a HTTP XML Namespace URI is made by including a
completed registration template in the IANA Considerations section of
an Internet-Draft.

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