Network Working Group M. Mealling
Internet-Draft VeriSign, Inc.
Expires: December 25, 2001 June 26, 2001
The IANA XML Registry
draft-mealling-iana-xmlns-registry-01.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This documenet describes an IANA maintained registry for IETF
standards which use XML related items such as Namespaces, DTD,
Schemas, and RDF Schemas.
1. Introduction
Over the past few years XML [2] has become a widely used method for
data markup. There have already been several IETF Working Groups
that have produced standards that define XML DTDs, XML Namespaces [3]
and XML Schemas [4]. Each one of these technologies uses URIs [1] to
identify their respective versions. For example, a given XML
document defines its DTD using the DOCTYPE element. This element,
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like SGML, has a PUBLIC and a SYSTEM identifier. It is standard
practice within W3C standards to forego the use of the PUBLIC
identifier in favor of 'well known' SYSTEM identifiers. There have
been several IETF standards that have simply created non-existent
URIs in order to simply identify but not resolve the SYSTEM
identifier for some given XML document.
This document seeks to standardize this practice by creating an IANA
maintained registry of XML elements so that document authors and
implementors have a well maintained and authoritative location for
their XML elements. As part of this standard, the IANA will both
house the public representation of the document and assign it a
Uniform Resource Name that can be used as the URI in any URI based
identification components of XML.
2. Registerable Documents
2.1 The Assigned URIs
All elements in this registry will have a URN of the form:
urn:iana:xml:<class>:<id>
where <class> is the type of the document being registered (see
below). <id> is a unique id generated by the IANA based on any means
the IANA deems necessary to maintain uniqueness and persistence.
The IANA will also maintain a file server available via at least HTTP
that contains all of the registered elements in some publicly
accessible file space (in the same way that all of the IANAs
registered elements are available via
http://www.isi.edu/in-notes/iana/assignments/).
2.2 Document Types
The list of types of XML documents that can be registered with the
IANA are:
dtd -- An XML document that contains a DOCTYPE element can identify
its DTD via both a PUBLIC identifier and a SYSTEM identifier. The
URN assigned by the IANA can be used as the value of the SYSTEM
identifier.
ns -- XML Namespaces [3] are named by a URI. They have no real,
machine-parseable representation other than the specifications
that define them. Thus the element registered will be the
specification (or a pointer to it). The URN assigned by the IANA
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will be the XML Namespace's name.
schema -- XML Schemas [4] are also identified by a URI but their
contents are machine parseable. The IANA registered document will
be the XML Schema file. The URN the IANA assigns can be used as
the URI for the schema.
rdfschema -- The Resource Description Format (RDF) [5] is an XML
serialization of a connected graph based data model used for
metadata expression. RDF makes use of schemas for RDF that
express grammars about relationships between URIs. These grammars
are identified by URIs. The URN assigned by the IANA can be used
as the identifying URI.
3. Registration Procedures
Until such time as the IANA requests or implements an automated
process for the registration of these elements, any specifications
wishing to do so must make that request part of the IANA
considerations section of their respective documents.
4. IANA Considerations
This documents seeks to create a rather large registry for which the
IANA (at the direction of the IESG) will primarily be responsible.
The amount of effort required to maintain this registry is not
insignificant and the policies and procedures surrounding any
approval process are non-trivial.
References
[1] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[2] WorldWideWeb Consortium, "Extensible Markup Language (XML) 1.0
(Second Edition)", W3C Recommendation, Available at
http://www.w3.org/TR/2000/REC-xml-20001006, October 2000.
[3] WorldWideWeb Consortium, "Namespaces in XML", W3C
Recommendation, Available at http://www.w3.org/TR/1999/REC-xml-
names-19990114/, January 1999.
[4] WorldWideWeb Consortium, "XML Schema Part 0: Primer", W3C
Recommendation, Available at http://www.w3.org/TR/xmlschema-0/,
May 2001.
[5] WorldWideWeb Consortium, "Resource Description Framework (RDF)
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Model and Syntax Specification", W3C Recommendation, Available
at http://www.w3.org/TR/REC-rdf-syntax/, February 1999.
Author's Address
Michael Mealling
VeriSign, Inc.
Mountain View, CA
US
EMail: michael@research.netsol.com
URI: http://www.research.netsol.com
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